A new PNG spec
programmax.net
programmax.net
- It isn't really a "new format". It's an update to the existing format. - It is very backwards compatible. -- Old programs will load new PNGs to the best of their capability. A user will still know "that is a picture of a red apple".
There also seems to be some confusion about how PNGs work internally. Short and sweet: - There are chunks of data. -- Chunks have a name, which says what data it contains. A program can skip a chunk it doesn't recognize. - There is only one image stream.
Chris Lilley--one of the original PNG co-authors--has a post with an example HDR image: https://svgees.us/blog/cICP.html It is about half way down, with the birthday cake. Generally, us tech nerds have phones that are capable of displaying it well. So perhaps view the page on your phone.
What you should look for is the cake, the pink tips in her hair, and the background being more vivid. For me, the pink in the cake was the big give-away.
There is also the Web Platform Tests (WPT) which we use to validate browser support: https://wpt.fyi/results/png/cicp-chunk.html?label=master&lab...
Although, that image is just a boring teal. See it live in your browser here: https://wpt.live/png/cicp-chunk.html
For an example of APNG, you can use Wikipedia's images: https://en.wikipedia.org/wiki/APNG
But you have a bigger point: I should have live demonstrations of those things to help people understand.
Sooooo file some bugs :D
Also, be kind to them. This literally launched yesterday.
There was nothing you could do about the TV, the screen couldn't show all the colors that you needed.
Pink can pose problems for individuals with red-green color blindness (or more exactly: color vision deficiency). So make sure that examples work for these people too. Otherwise the examples might not work for about 8% of your male viewers.
For the lifetime of PNG so far, a PNG file has almost, but just barely not, been a valid Interchange File Format (IFF) file.
IFF is a great (simple to understand, simple to implement support for, easy to generate, easy to decode, memory-efficient, IO-efficient, relatively compact, highly compressible) metaformat, that more people should be aware of.
However, up to this point, the usage of IFF has consisted of:
• some old proprietary game-data and image formats from the 1980s that no modern person has heard of
• some popular-yet-proprietary AV formats [AIFF, RIFF] that nobody would write a decoder for by hand anyway (because they would need a DSP library to handle the resulting sample-stream data anyway, and that library may as well offer container-format support too)
• The object files of an open but uncommon language runtime (Erlang .beam files), where that runtime exposes only high-level domain-specific parsing tooling (`beam_lib`) rather than IFF-general decoding tooling
• An "open-source but corporate-steered" image format that people are wary of allowing to gain ecosystem traction (WebP — which is more-specifically a document in a RIFF container)
• And PNG... but non-conformantly, such that any generic IFF decoder that could decode the other things above, would choke on a PNG file.
IMHO, this is a major reason that there is no such thing as "generalized IFF tooling" today, despite the IFF metaformat having all the attributes required to make it the "JSON of the binary world". (Don't tell me about CBOR; ain't nobody hand-rolling a CBOR encoder out of template strings.)
If you can't guess by now, my wishlist item for PNGv3, is for PNG files to somehow become valid/conformant IFF files — such that the popularity of PNG could then serve as the bootstrap for a real IFF tooling ecosystem, and encourage awareness/use of IFF in new greenfield format-definition use-cases.
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Now, I've written PNG parsers, and generic IFF parsers too. I've even tried this exact unification trick before (I wanted an Erlang library that could parse both .beam files and PNG files. $10 if you can guess the use-case for that!)
Because of this, I know that "making PNG valid per IFF" isn't really possible by modifying the PNG format, while ensuring that the resulting format is decodable by existing PNG decoders. If you want all the old [esp. hardware] PNG parsers to be compatible with PNGv3s, then y'all can't exactly do anything in PNGv3 like "move the 4-byte CRC inside the chunk as measured by the 4-byte chunk length" or "make the CRCs into their own chunks that reference the preceding record".
But I'm not proposing that. I'm actually proposing the opposite.
Much of what PNGv2 did in contravention of the IFF spec, is honestly a pretty good idea in general. It's all stuff that could be "upstreamed" — from the PNG level, to the IFF level.
I propose: formalizing "the variant of IFF used in PNG" as its own separate metaformat specification — breaking this metaformat out from the PNG spec itself into its own standards document.
This would then be the "Interchange File Format specification, version 2.0" (not that there was ever a formal IFFv1 spec; we all just kind of looked at what EA/Commodore had done, and copied it in our own code since it was so braindead-easy to implement.)
This IFF 2.0 spec would formalize, at least, a version or "profile" of IFF for which PNGv2 images are conformant files. It would have chunk CRCs; chunk attribute bits encoded for purposes of decoders + editors via meaningful chunk-name letter-casing; and an allowance for some number of garbage bytes before the first valid chunk begins (for PNG's leading file signature that is not itself a valid IFF chunk.)
This could be as far as the IFF 2.0 spec goes — leaving IFFv1 files non-decodable in IFFv2 parsers. But that'd be a shame.
I would suggest going further — formalizing a second IFFv2 "profile" against which IFFv1 documents (like AIFF or RIFF files) are conformant; and then specifying that "generic" IFFv2-conformant decoders (i.e. a hypothetical "libiff", not a format-specific libpng) MUST implement support for decoding both the IFFv1-conforming and the PNGv2-conforming profiles of IFF.
It could then be up to the IFF-decoding-tooling user (CLI command user, library caller) to determine which IFFv2 "profile" to apply to a given document... or the IFFv2 spec could also specify some heuristic algorithm for input-document "profile" detection. (I think it'd be pretty easy; find a single chunk, and if what follows its chunk-length is a CRC that validates that chunk, then you have the PNGv2-like profile. Whereas if it's not that, but is instead four bytes of chunk-name-valid character ranges, then you've got the IFFv1-like profile. [And if it's neither, then you've got a file with a corrupted first chunk.])
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And, if you want to go really far, you could then specify a third entirely-novel "profile", for use in greenfield IFF applications:
• A few bytes of space aren't so precious; we can hash things much faster these days, with hardware-accelerated hashing instructions; and those instructions are also for hashes that do much better than CRC to ensure integriaty. So either replace the inline CRCs with CRC chunks, or with nested FORM-like container records (WCRC [len] [CRC4] [interior chunk]). Or just skip per-chunk CRCs and formalize a fHsh chunk for document-level integrity, embedding the output of an arbitrary hash algorithm specified by its registered https://github.com/multiformats/multihash "hash function code".
• Re-widen the chunk-name-valid character set to those valid in IFFv1 documents, to ensure those can be losslessly re-encoded into this profile. To allow chunks with non-letter characters to have a valid attribute decoding, specify a document-level per-chunk-name "attributes of all chunks of this type" chunk, that can either be included into a given concrete format's header-chunk specification, or allowed at various points in the chunk stream per a concrete format's encoding rules (where it would then be expected to apply to any successor + successor-descendant chunks within its containing chunk's "scope.") Note that the goal here is to keep the attribute bits in some way or another — they're very useful IMHO, and I would expect an IFF decoder lib to always be emitting these boolean chunk-attribute fields as part of each decoded chunk.
• Formalize the magic signature at the beginning into a valid chunk, that somehow encodes 1. that this is an IFF 2.0 "greenfield profile" document (bytes 0-3); 2. what the concrete format in use is (bytes 4-7). (You could just copy/generalize what RIFF does here [where a RIFF chunk has the semantics of a LIST chunk but with a leading 4-byte chunk-name type], such that the whole document is enclosed by a root chunk — though this is painful in that you need to buffer the entire document if you're going to calculate the root-chunk length.)
I'm just spitballing; the concrete details of such a greenfield profile don't matter here, just the design goal — having a profile into which both IFFv1 and PNGv2 documents could be losslessly transcoded. Ideally with as minimal change to the "wider and weirder/more brittle ecosystem" side [in this case that's IFFv1] as possible. (Compare/contrast: how HTML5 documents are a profile of HTML that supersedes both HTML4 and XHTML1.1 — supporting both unclosed tags and XML-namespaced element names — allowing HTML4 documents to parse "as" HTML5 without rewrites, and XHTML1.1 documents to be transcoded to HTML5 by just stripping some root-level xmlns declarations and changing the doctype.)
W3C requires that we do not break old, conformant specs. Meaning if the next PNG spec would invalidate prior specs, they won't approve it. By extension, an old, conformant program will not suddenly become non-conformant.
I could see a group of people formalizing IFFv2, and adapting PNG to it. But that would effectively be PNGIFF, not PNG. It would be a new spec. Because we cannot break the old one.
That might be fine. But it comes with a new set of problems, like adoption.
Soooo I like the idea but it would probably be a separate thing. FWIW, it would actually be nice to make a formal IFF spec. If there was no governing body that owns it, we can find an org and gather interest.
I doubt W3C would be the right org for it. ISO subgroup??
It's also questionable how much you actually benefit from common container formats like this since you need to know the application specific format contained anyway in order to do anything useful with it. It also causes problems where "smart" programs treat files in ways that make no sense, e.g. by offering to extract a .docx file just because it looks like a .zip
One neat thing about IFF is that all of its "container" chunk types (LIST, FORM, CAT) are part of the standard; the expectation is that domain-specific chunk types should [mostly] be leaf nodes. As such, IFF is at least "legible" in the same way that XML or JSON or Lisp is legible (and more than e.g. ELF is legible): you're meant to decompose an object graph into individual IFF chunks for each object in the graph. Which translates to IFF files being "browseable", rather than dead-ending in opaque tables that require some other standard to tell how how they're even row-delimited.
Another neat thing is that, like with namespaced XML element names, chunk names — at least the "public" ones — are meant to have globally-unique meanings, being registered in a global registry (https://wiki.amigaos.net/wiki/IFF_FORM_and_Chunk_Registry). This means that IFF tooling can "browse" an arbitrary unknown IFF document, find a chunk it does understand the meaning of, and usefully decode it (and maybe its descendants) for you.
Many more-complex IFF formats (e.g. the AV containers like RIFF) embed data of other media types as chunks of these registered types. Think "thumbnail in a video file" or "texture in a scene file." Your tooling doesn't need to know the semantics of the outer format, to be able to discover these registered inner chunks inside it, and browse/preview/extract them. (Or replace them one-for-one with another asset of the same type; or even, if they're inside a simple LIST chunk, add or remove instances of the asset from the list!)
Also, somewhat interestingly, given the way IFF is structured, there is no inherent difference between embedding a sub-resource "opaquely" vs embedding it "legibly" — i.e. if you embed a [headerless] IFF document as the value of a chunk in another IFF document, then that's exactly the same thing as nesting the root-level chunk(s) of that sub-document within the parent chunk. It's like how an SVG sub-document inside an XHTML document isn't a separate serialized blob that gets sucked out and parsed, but rather just additional tags in the XHTML document-string, around which a boundary of "this is a separate XML sub-document" gets drawn by some "DOM document builder" code downstream of the actual XML parser.
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But besides the technical "it can be done" points, let me also speak more in terms of the motivation. Why would you want to?
Well, have you ever wanted to open up a complex file and pull its atomic-level assets out? Your first thought when hearing that was probably "that sounds like a nightmare" — and yes, today, it is.
But back in the 1980s, with the original growth of IFF-based formats, we temporarily lived in this wonderland where there were all these different browseable / explorable file formats, that could be cracked open with exactly the same tools.
Do you wonder how and why the game modding scene first came into existence? It was basically the result of games storing their asset packs in these simple-to-parse/generate file formats — where people could easily drop-in replace one of those assets with a new one with simple command-line tools, or even with a GUI, without worrying about matching asset sizes / binary offset patching / etc — let alone with any knowledge of how the container file format works.
Do you appreciate how macOS app bundles just have a browseable, hierarchical Resources directory inside them? Before app bundles, macOS applications held their resources in a "resource fork" — essentially a set of FourCC-tagged file extended-attributes (though actually, a single on-disk packfile that acted as a random-access key-value store of those xattrs). And both of these approaches (bundle Resources dirs, and resource forks) provided the same explorability / moddability as IFF files do. People would throw a macOS program into ResEdit and pull out its icons, its fonts, its strings, whatever — where those weren't program-domain-specific things, but rather were effectively items with standardized media types (their FourCC codes being effectively the predecessor of modern MIME types.)
For that matter, consider this quote from the IFF wiki page:
> There are standard chunks that could be present in any IFF file, such as AUTH (containing text with information about author of the file), ANNO (containing text with annotation, usually name of the program that created the file), NAME (containing text with name of the work in the file), VERS (containing file version), (c) (containing text with copyright information).
Now, remember that IFF decoders are almost always expected / coded to ignore chunks they don't understand. (Especially for IFF files encoded as a toplevel stream of heterogeneous chunk types.)
That means that not only can various format authors decide to use these standard chunks... but third-party editors can also just drop chunks like this into the things they edit! You know how Windows has that "name, author, version" etc info on the Properties sheet for some file types? That info could show up and be editable for any IFF-based file format — whether the particular format has an "allowance" for it or not.
(There's nothing special about IFF here, by the way. You could just as well drop "foreign-namespaced attributes" like this into an e.g. XML-based document format. The difference is a cultural one: the developers of XML-based document formats tend to have their XML decoders validate their documents for strict conformance to an XML schema; and XML schemas tend to be [but don't have to be!] designed as whitelists of the possible tags that can be used within any given parent nesting path. IFF, meanwhile, has never had anything like a schema-based document validation. Every document was best-effort parsed, like HTML4; and so every IFF-based format decoder is a best-effort decoder, like a web browser parsing HTML4. That very lack of schema-based validation, actually opens up a lot of use-cases for IFF.)
> We really shouldn't be making new standards with big endian byte order.
IFF isn't a wire protocol standard for efficient zero-copy; and nor is it intended for file formats amenable to being streaming-parsed.
And that's okay! Not every format needs to be suited to efficient, scalable, concurrent, [other lovely words] message passing!
IFF has two major use-cases:
1. documents that are "loaded" in some program, where "loading" is expected to occur against a random-access block device; where each chunk will be visited in turn, with either its contents being parsed into an in-memory representation; its contents' slicing bounds being stored to later stream or random-access within (or the part of the file within those bounds being mmap(2)ed — same thing); or that chunk discarded, thus allowing the load operation to skip issuing any read ops for it or its descendants entirely.
This is the PNG use-case.
(Though, interestingly enough, since PNG has only one large chunk — the image data — PNG can be made into an "effectively-streamed format" simply by keeping that big chunk at the end of the IFF document. Presuming the stream length of the PNG file is known [as in a regular HTTP fetch], the "skeleton load" process for PNG can terminate after just having parsed its way through all the other tiny chunks — perhaps with a few minimal buffer waits to skip over unknown chunks — but with no need to buffer the entire image data chunk. [It adds the image-data-chunk length to the file pointer, realizes there's no more room for chunks in the stream, and so doesn't bother to buffer+seek past that final chunk.] The IFF parser then returns to the caller, passing it the slicing bounds of [among other things] the (still not-yet-fully-received) image-data chunk. And the caller can then turn around, and hand the same FILE pointer and those slicing bounds to its streaming renderer, letting it go to town consuming the stream as needed.)
IFF in its skeleton-loading model, would also be ideal for something like e.g. a font file (which has lots of little tables, which are either eagerly parsed, or ignored, by any given renderer.)
2. simple "read-rarely" packfile documents, that act sort of like little databases, but without any sort of TOC header part; where, when you want to grab something from the packfile, you re-navigate down through it from the root, taking the IOPS hit from all the seeks to each nesting-parent chunk's preceeding sibling chunks before hitting the descendant you want to navigate into.
This is the use-case of most IFFv1 file formats — most of them were made for use by programs that would grab this or that for the program's use either once at startup, or when the thing became relevant. (Think of the types of things a Windows executable embeds as "resources" — icons, translated strings, XAML declarative-MVC-view documents, etc.)
For a parallel, IFF here is to "using an entire archive-format library like tar or zip to store these assets for random access", as "spitting CSV/XML out using template strings" is to using a library to encode a table to a Parquet/ORC/etc. table.
The parallel is that in both cases, you're trading some performance and robustness, for massively reduced complexity and ease of implementation. Like with emitting CSV, you can slop together an IFF encoder right there inside your data-emitting logic — in any language that can write out binary files, and without even having access to the Internet, let alone adding a dependency on an encoder package in some package ecosystem. You can do it in C; you can do it in assembly; you can do it in a bash script; you can do it in BASIC; you can do it in a Windows batch file; you can do it in your single-file Python or Ruby or Perl script that lives in your repo. You can probably do it in a Makefile!
(Also, given how IFF parsing works [i.e. given that any given chunk's contents is in superposition of being either an opaque binary slice or a potential stream of child chunks, with a streaming event-based parser able to decide at each juncture whether to take that step of decoding the child chunks or to leave them as an undecoded binary for now], if you start to care about performance, you can just stick some memoization in front of your "fetch a key-path-lens KP from document D" function, and now you're building a just-in-time TOC. And obviously you can put TOC chunks in your IFF-based file formats if you want — though IMHO doing so kind of goes against the spirit of IFF.)
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In neither of those use-cases does it really matter that lengths require reading four bytes one-at-a-time with left-shifts, rather than being able to just plop the four bytes into a register. These aren't cases where the parse overhead of the the structural glue between the data, will ever be non-trivial relative to the time it takes to consume the data itself.
And even if you did want to use IFF for something crazy, like as a substitute for Protobuf: did you know that most modern CPU ISAs have a byte-shuffle instruction that can transform big-endian into little-endian [among an unbounded number of other potential transformations] in a single cycle? Endian-ness did matter in protocol design for a while... but these days, unless you're e.g. a Google engineer designing a new SAN protocol, and optimizing it for message-handling overhead on your custom SDN L7 network-switch silicon that doesn't have a shuffle op... endian-ness is mostly irrelevant again!
This is great but also has the issue that users might not notice that their setup is giving them a less than optimal result. Of course that is probably still better than not having backwards compatibility.
Edit: Seems the backwards compatibility isn't as great as it could be. Old programs show a washed out image instead which sucks. This should have been avoidable in the same way JPG gain maps work so that you only need updated programs to take advantage of the increased gamut on more-than-sRGB screens and not to correctly show colors that fit into sRGB.
However, gain maps are extra data. So there is a trade off.
The reason gain maps didn't make it into Third Edition is it isn't yet a formal standard. We have a bunch of the work ready to go once their standard launches.
The big one is adoption. I love JPEG XL and hope it becomes more widely adopted. It is very scary to add a format to a browser because you can never remove it. Photoshop and MSPaint no longer support ICO files, but browsers do. So it makes sense for browsers to add support last, after it is clearly universal. I think JPEG XL is well on their way using this approach. But they aren't there yet and PNG is.
There is also longevity and staying power. I can grab an ancient version of Photoshop off eBay and it'll support PNG. This also benefits archivists.
As a quick side note on that: I want people to think about their storage and bandwidth. Have they ever hit storage/bandwidth limits? If so, were PNGs the cause? Was their site slow to load because of PNGs? I think we battle on file size as an old habit from the '90s image compression wars. Back then, we wanted pixels on the screen quickly. The slow image loads were noticeable on dial-up. So file size was actually important then. But today?? We're being penny-wise and pound-foolish.
What sort of improvements might we expect? Is there a chance of it rivalling lossless WebP and JPEG XL?
You can see this with PNG optimizers like OptiPNG and pngcrush.
So step 1 is to improve libpng. This requires no spec change.
Step 2 is to enable parallel encoding and decoding. We expect this to increase the file size, but aren't sure how much. It might be surprisingly small (a few hundred bytes?). It will be optional.
Step 3 is the major changes like zstd. This would prevent a new PNG from being viewable in old software, so there is a considerably higher bar for adoption. If we find step 1 got us within 1% of zstd, it might not be worth such a major change.
I don't yet know what results we'll find or if all the work will be done in time. So please don't take this as promises or something to expect. I'm just being open and honest about our intentions and goals.
https://dev.exiv2.org/projects/exiv2/wiki/The_Metadata_in_PN...
This is similar to HTTP request headers, if you're familiar with that. There are a set of standard headers (User-Agent, ETag etc) but nobody is stopping you from inventing x-tomtom and sending that along with HTTP request. And on the receiving end, you can parse and make use of it. Same thing with PNG here.
Yes, a hypothetical user's sprinker layout "map" or whatever they're working on is actually composed of a few rectangles that represent their house, and a spline representing the garden border, and a circle representing the tree in the front yard, and a bunch of line segments that draw the pipes between the sprinkler heads. Yes, each of those geometric elements can be concisely defined by JSON text that defines the X and Y location, the length/width/diameter/spline coordinates or whatever, the color, etc. of the objects on the map. And yes, OP has a rendering engine that can turn that JSON back into an image.
But when the user thinks about the map, they want to think about the image. If a landscaping customer is viewing a dashboard of all their open projects, OP doesn't want to have to run the rendering engine a dozen times to re-draw the projects each time the page loads just to show a bunch of icons on the screen. They just want to load a bunch of PNGs. You could store two objects on disk/in the database, one being the icon and another being the JSON, but why store two things when you could store one?
[1] - https://github.com/Draneria/Metallics-by-Draneria_Krita-Brus...
[2] - https://krita-artists.org/t/memileo-impasto-brushes/92952/11...
But you did need to remember to export if you didn't want the extra fields increasing the file size. I remember finding fireworks pngs on web pages many times back then.
Also, Adobe saves AI files into a PDF (every AI file is a PDF file), and Photoshop can save PSD files into TIFF files (people wonder why these TIFFs have several layers in Photoshop, but just one layer in all other software).
Fireworks was my favorite image editor, I don't know that I've ever found one I love as much as I loved Fireworks. I'm not a graphics guy, but Fireworks was just fantastic.
https://community.adobe.com/t5/fireworks-discussions/open-fi...
(Not many things handle .ai so well either!!)
Can you compress it? I mean, theoretically there is this 'zTXt' chunk, but it never worked for me, therefore I'm asking.
Really, I think its pretty common for tools that work with images generally.
Assuming Next gen PNG will still require new decoder. They could just call it PNG2.
JPEG-XL already provides everything most people asked for a lossless codec. If there are any problems it is its encoding and decoding speed and resources.
Current champion of Lossless image codec is HALIC. https://news.ycombinator.com/item?id=38990568
And this will improve over time, like jpg encoders and decoders did.
When it comes to hardware encoding/decoding, I am not following your point I think. The fact that some are already looking at hardware implementation for JPEG XL means that….?
I just know JPEG hardware acceleration is quite common, hence I am trying to understand how that makes JPEG XL different/better/worse?
Hardware acceleration for lossless makes more sense for JPEG XL because it is currently very slow. As the author of HALIC posted some results below, JPEG XL is about 20 - 50x slower while requiring lots of memory after memory optimisation. And about 10 - 20 times slower compared to other lossless codec. JPEG XL is already used by Camera and stored as DNG, but encoding resources is limiting its reach. Hence hardware encoder would be great.
For lossy JPEG XL, not so much. Just like video codec, hardware encoder tends to focus on speed and it takes multiple iteration or 5 - 10 years before it catches up on quality. JPEG XL is relatively new with so many tools and usage optimisation which even current software encoder is far from reaching the codec's potential. And I dont want crappy quality JPEG XL hardware encoder, hence I much prefer an upgradeable software encoder for JPEG XL lossy and hardware encoder for JPEG XL Lossless.
[1] https://encode.su/threads/4025-HALIC-(High-Availability-Loss...
It looks like LEA 0.5 is the champion.
And HALIC is not even close to ten in this [2] lossless image compression benchmark.
[2] https://github.com/WangXuan95/Image-Compression-Benchmark
Are there usecases for lossless other than archival?
A lot of images should be lossless. Icons/pictograms/emoji, diagrams and line drawings (when rasterized), screenshots, etc. You can sometimes get away with large-resolution lossy for some of these if you scale it down, but that doesn't necessarily translate into a smaller file size than a lossless image at the intended resolution.
There's another problem with lossy images, which is re-encoding. Any app/site that lets you upload/share an image but also insists on re-encoding it can quickly turn it into pixelated mush.
WebP is amazing. But if I were going to label something "state of the art" I would go with JPEGXL :)
For myself, I use PNG only for computer-generated still images. I tend to use good ol' JPEG for photos.
Apart from the widespread support in codecs, there are 3 important elements: processing speed, compression ratio and memory usage. These are taken into account when making a decision (pareto limit). In other words, the fastest or the best compression maker alone does not matter. Otherwise, the situation can be interpreted as insufficient knowledge and experience about the subject.
HALIC is very good in lossless image compression in terms of speed/compression ratio. It also uses a comic amount of memory. No one mentioned whether this was necessary or not. However, low memory usage negatively affects both the processing speed and the compression ratio. You can see the real performance of HALIC only on large-sized(20 MPixel+) images(single and multi-thread). An example current test is below. During operations, HALIC uses only about 20 MB of memory, while JXL uses more than 1 GB of memory.
https://www.dpreview.com/sample-galleries/6970112006/fujifil...
June 2025, i7 3770k, Single Thread Results
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First 4 JPG Images to PPM, Total 1,100,337,479 bytes
HALIC NORMAL: 5.143s 6.398s 369,448,062 bytes
HALIC FAST : 3.481s 5.468s 381,993,631 bytes
JXL 0.11.1 -e1: 17.809s 28.893s 414,659,797 bytes
JXL 0.11.1 -e2: 39.732s 26.195s 369,642,206 bytes
JXL 0.11.1 -e3: 81.869s 72.354s 371,984,220 bytes
JXL 0.11.1 -e4: 261.237s 80.128s 357,693,875 bytes
----------------------------------------------------
First 4 RAW Images to PPM, Total 1.224.789.960 bytes
HALIC NORMAL: 5.872s 7.304s 400,942,108 bytes
HALIC FAST : 3.842s 6.149s 414,113,254 bytes
JXL 0.11.1 -e1: 19.736s 32.411s 457,193,750 bytes
JXL 0.11.1 -e2: 42.845s 29.807s 413,731,858 bytes
JXL 0.11.1 -e3: 87.759s 81.152s 402,224,531 bytes
JXL 0.11.1 -e4: 259.400s 83.041s 396,079,448 bytes
----------------------------------------------------
I had a very busy time with HALAC. Now I've given him a break, too. Maybe I can go back to HALIC, which I left unfinished, and do better. That is, more intense and/or faster. Or I can make it work much better in synthetic images. I can also add a mode that is near-lossless. But I don't know if it's worth the time I'm going to spend on it.
Strictly true, but e.g. for archival or content delivered to many users compression speed and memory needed for compression is an afterthought compared to compressed size.
Probably the best news here. While you already can write custom data into a header, having Exif is good.
BTW: Does Exif have a magnetometer (rotation) and acceleration (gravity) field? I often wonder about why Google isn't saving this information in the images which the camera app saves. It could help so much with post-processing, like with leveling the horizon or creating panoramas.
Old decoders and new decoders now could render an image with exif rotation differently since it's an optional chunk that can be ignored, and even for new decoders, the spec lists no decoder recommendations for how to use the exif rotation
It does say "It is recommended that unless a decoder has independent knowledge of the validity of the Exif data, the data should be considered to be of historical value only.", so hopefully the rotation will not be used by renderers, but it's only a vague recommendation, there's no strict "don't rotate the image" which would be the only backwards compatible way
With jpeg's exif, there have also been bugs with the rotation being applied twice, e.g. desktop environment and underlying library both doing it independently
The camera knows which way it's oriented, so it should just write the pixels out in the correct order. Write the upper-left pixel first. Then the next one. And so on. WTF.
If a smartphone camera is doing it, then bad camera app!
This is particularly important on smartphones and battery operated devices. However, most smartphone devices simply save the photo the same way regardless of orientation, and simply add a display-rotated flag to the metadata.
It can be super annoying sometimes, as one can't really disable the feature on many devices. =3
It's basically a shame that the exif metadata contains things that affect the rendering
Could you explain this one?
What are the arguments for this? It would seem easier for everyone to rotate and then store exif for the original rotation if necessary.
Performance. Rotation during rendering is often free, whereas the camera would need an intermediate buffer + copy if it's unable to change the way it samples from the sensor itself.
The hardware likely is optimized for the common case, so I would think that can be a lot slower. It wouldn’t surprise me, for example, if there are image sensors out there that can only be read out in top to bottom, left to right order.
Also, with RAW images and sensors that aren’t rectangular grids, I think that would complicate RAW images parsing. Code for that could have to support up to four different formats, depending on how the sensor is designed,
Your raw-image idea is interesting. I'm curious as to how photosites' arrangement would play into this.
RAW images aren't JPEGs so not relevant to the discussion.
Exif fields: https://exiv2.org/tags.html
And is being able to read an image without an opt-in tag something that has to be explicitly enabled in the reference implementation's API?
You could store this in Exif.Photo.MakerNote: "A tag for manufacturers of Exif writers to record any desired information. The contents are up to the manufacturer." I think it can be pretty big, certainly more than enough for 9 DoF position data.
Curious if Animated SVGs are also a thing. I remember seeing some Javascript based SVG animations (it was a animated chatbot avatar) - but not sure if there is any standard framework.
Yes. Relevant animation elements:
• <set>
• <animate>
• <animateTransform>
• <animateMotion>
Given how often it is used as a jargon term in software development, I can absolutely see this usage of "use-case" here as a "vote" for the next step in the process. Will we eventually see "usecase" become common? It's possible. I think it might even be a good idea. I'm debating adding my own "votes" for the hyphen moving forward.
Most other SVG renderers don't support much CSS.
This could possibly be used to build full fledged games like pong and breakout :)
https://shkspr.mobi/blog/2025/06/an-annoying-svg-animation-b...
Can animated PNG beat av1 or whatever?
[0] like for example these old Windows animations: https://www.randomnoun.com/wp/2013/10/27/windows-shell32-ani...
The AV1 spec [1] does not allow RGB color spaces, therefore AV1 cannot preserve RGB animations in a bit-identical fashion.
It is a bit-reversible rotation of the RGB cube. It makes the channels look more like luma and chroma that the codec expects.
8-bit YCoCg (even when using the reversible YCoCg-R [1] scheme) cannot represent 8-bit RGB losslessly. The chroma channels would need 9 bits of precision to losslessly recover the original 8-bit RGB values.
[1] https://www.microsoft.com/en-us/research/wp-content/uploads/...
It's also possible to directly encode RGB (channels ordered as GBR) when you set identity matrix coefficients, it's just less efficient.
I've implemented this in my AVIF encoder, so I know what I'm saying.
For video content maybe. Pixel-art gifs are not something video codecs do well at without introducing lots of artifacts.
Animated PNGs can't beat GIF nevermind video compression algorithms.
In APNG it's either the same 256 colors for the whole animation, or you have to use 24-bit color. That makes the pixel data 3 times larger, which makes zlib's compression window effectively 3 times smaller, hurting compression.
OTOH GIF can add 256 new colors with each frame, so it can exceed 256 colors without the cost of switching all the way to 16.7 million colors.
Not entirely true, it depends on what's being displayed, see a few simple tests specifically constructed to show how much better APNG can be vs GIF and {,lossy} webp: http://littlesvr.ca/apng/gif_apng_webp.html
Of course I don't think it generalizes all that well…
edit: using the same ezgif webp and apng on a H.264 source, apng is suddenly 10x the size than webp. It seems apng is only better if the source is gif
That's not really true. Some websites lie to you by putting .gif in the address bar but then serving a file of a different type. File extensions are merely a convention and an address isn't a file name to begin with so the browser doesn't care about this attempt at end user deception one way or the other.
I'm not sure why people disagree so strongly with what I wrote. Worst case scenario is that it's a slightly tangential but closely related rant about deceptive web design practices. Best case scenario is that someone who thought some sort of fancy trick involving gifs was in use learns something new.
They just don't have a proper UI and JS APIs exposed, and there's nothing stopping them from adding that.
IMO browsers are just stuck with tech debt, and maintainin a no-longer-relevant distinction between "animations" and "videos". Every supported codec should work wherever GIF/APNG work and vice versa.
It's not even a performance or complexity issue, e.g. browsers support AVIF "animations" as images, even though they're literally fully-featured AV1 videos, only wrapped in a "pretend I'm an image" metadata.
Browsers should just allow animated gifs and apngs in <video>
It's a shame that browser vendors didn't add silent looping video support to the img tag over (imo) baseless concerns.
SVG is just html5, it has full support for CSS, javascript with buttons, web workers, arbitrary fetch requests, and so on (obviously not supported by image viewers or allowed by browsers).
If you use an <img> tag, svgs are loaded in "restricted" mode. This disables scripting and external resources. However animation via either SMIL or CSS is still supported.
Nowadays, AVIF serves that purpose best I think.
AVIF is only starting to become widespread so can't be used without fallback if you care about your users. Not sure how it compares to AV1 quality/compression wise but hopefully its not as gimped as webp and there will encoders that aren't as crap as libwebp that almost everyone uses.
The fact that we have the <img> element at all is bad. HTML has since the early days a perfectly capable <object> which can even be nested to provide fallback, but browser support was always spotty.
The Acid2 test famously used <object> to shame browser vendors into supporting it at least to some extent.
Also while true color gifs seem to be possible it is usually limited to 256 colors per image.
For those reasons alone APNG is much better than GIF.
No, it's limited to 256 colors per frame and frames can have duration 0 which allows you to combine multiple frames into more than 256 color images.
I'm not sure about the tools and DX around animated PNGs. Is that a thing?
You can even have one frame that gets shown if and only if animation is not supported.
It is never shown by compliant apng decoders. You can make it the first frame of the animation, or any other image you want. e.g. some text saying "APNG unsupported"
Not progressively though unless browsers add a new mime type for it which they did not bother to do with animated webp.
There is just no need for a PNG update, just adopt JPEG XL.
I've not tried it on images, but wouldn't zstandard be exceedingly bad at gradients? It completely fails to compress numbers that change at a fixed rate
Bzip2 does that fine, not sure why https://chaos.social/@luc/114531687791022934 The two variables (inner and outer loop) could be two color channels that change at different rates. Real-world data will never be a clean i++ like it is here, but more noise surely isn't going to help the algorithm compared to this clean example
Maybe I sounded too critical of zstd. To be clear: I use it for general-purpose compression where available, the only exception would be where eeking out the last % gain is important and slow decompression is acceptable and it has one of these patterns that Bzip2 does better in the first place
That it's better than deflate (afaik aka gzip and zlib, just with different header fields) is not surprising since that was iirc the defined goal of Zstandard project
It also has pretty much every feature desired in an image standard. It is future-proofed.
You can losslessly re-compress a JPEG into a JPEG-XL file and gain space.
It is a worthy successor (while also being vastly superior to) JPEG.
Not sure what the previous poster meant with “backward compatible” here. jxl is a different format. It can include every information a jpeg includes, which then maybe qualifies as “backward compatible” but it still is a different format.
Original JPEG -> JPEG XL -> Recreated JPEG.
Sha256(Original JPEG) == Sha256(Recreated JPEG).
That's what people meant by "backward compatible".
So backwards-compatible in the sense that the jpeg-xl algorithm spec can read jpg and store the same pixel data more efficiently as jxl if you like. You gain space and lose nothing (except perhaps encode/decode speed).
Is that gained space enough to account for the fact you now have 2 files? Sure, you can delete the original jpg on the local system, but are you going to purge your entire set of backups?
Unless serving jxl and saving bandwidth, while increasing your total storage, is worth it to you.
Also backup storage is usually cheaper than something that needs to have fast access speeds.
You'll know JPEG-XL if real when camera manufactures allow for XL acquisition instead of legacy JPEG only.
But they can recover them from the JXL files, so are they really “tossed out”? It’s not really different than any other form of lossless compression.
No one can afford to "just". Five years later and it's only one browser! Crazy.
Browser vendors must deliver, only then it's okay to admonish an end user or Web developer to adopt the format.
Tell that to Google. They gave up on XL in Chrome[1] and essentially killed its adoption.
It is only a matter of time until the Chrome team has to reverse their decision.
JPEG-XL's lossy modular mode is a very unique feature which needs a lot more exposure than it has. It is well-suited to non-photographic drawings or images that aren't continuous, and have never touched any JPEG-like codecs. It has different kinds of artifacts than what you typically see in a DCT image codec. Rather than ringing, you get slight pixellation.
JPEG XL has an edge-preserving filter ("EPF") for the purpose of reducing ringing.
Try opening a HEIC or AV1 or something on a machine that doesn't natively support it down to the OS-level, and you're in for a bad time. This stuff needs to work everywhere—in every app, in the OS shell for quick-looking at files, in APIs, on Linux, etc. If a codec does not function at that level, it is not functional for wider use and should not be a default for any platform.
But this is a feature. Think about all those exploits made possible by this feature. Sincerely, the CIA, the MI-6, the FSB, the Mossad, etc.
"photo scanned in 2025, is about something in easter, before 1940 and after 1920"
The usual sidecar files, XMP files, are standardised (in that they follow a certain extensible XML structure) and can (and often do) include EXIF file information.
[0] https://en.wikipedia.org/wiki/Extensible_Metadata_Platform
For ambiguous dates there is the EDTF Spec[1] which would be nice to see more widely adopted.
[0] https://www.media.mit.edu/pia/Research/deepview/exif.html
Different software reacts in different ways to partial specifications of yyyy/mm/dd such that you can try some of the cute tricks but probably only one s.w. package honours it.
And the majors ignore almost all fields other than a core set of one or two, disagree about their semantics, and also do wierd stuff with file name and atime/mtime.
cICP is 16 bytes for identifying one out of a "list of known spaces" but they chose not to include a couple of the most common ones. Off to a great start...
I wonder if it's some kind of legal issue with Adobe. That would also explain why EXIF / DCF refer to Adobe RGB only by the euphemism "optional color space" or "option file". [1]
[1] https://en.wikipedia.org/wiki/Design_rule_for_Camera_File_sy...
Maybe iccMAX supports HDR. I'm not sure. In either case, that isn't what PNG supported.
So something new was required for HDR.
How so? As far as I can tell, the ICCv2 spec is very agnostic as to the gamut and dynamic range of the output medium. It doesn't say anything to the extent of "thou shalt not produce any colors outside the sRGB gamut, nor make the white point too bright".
Unless HDR support is supposed to be something other than just the primaries, white point, and transfer function. All the breathless blogspam about HDR doesn't make it very clear what it means in terms of colorspaces.
I don't doubt that there's lots of problems in the chain from RGB samples to display output, but I'm finding this whole thing horribly confusing. Wikipedia tries to distinguish 'HDR' transfer functions like PQ [0] from 'SDR' transfer functions in terms of their absolute luminance, but the ICC specs are just filled with relative values all the way down.
(Not to mention how much these things get fiddled with in practice. Once, I had the idea of writing a JPEG decoder, so I looked into how exactly to convert between sRGB and Rec. 601 YCbCr coordinates. I thought, "I know, I'll just use the standard-defined XYZ conversions to bridge between them!" But psych, the ICC sRGB profile has its own black point scaling that the standards don't tell you about. I'm still not sure what the correct answer is for "these sRGB coordinates represent the exact same color as these Rec. 601 YCbCr coordinates".)
Here is what I can tell you confidently: The original plan was to provide an ICC profile that approximates PQ as best as we could. But it wasn't enough. So the proposal was to force the profile name to be a special string. When a PNG decoder saw that name, it would ignore the ICC profile and do actual PQ.
Here is that original proposal: https://w3c.github.io/png-hdr-pq/
Possibly more context (I just found this) from Apple. I'm not sure of date: https://www.color.org/hdr/02-Luke_Wallis.pdf Slide 29: "HDR parametric transfer functions not in ICC spec Parametric 3D tone mapping functions not in ICC spec - Neither can be approximated by 1-D or 3-D LUTs"
I'm not sure why they cannot be approximated by LUT. Maybe because of the inversion problem?
- In ICC-land, all luminances are relative to the display's (or reflective medium's) black and white points. So for an HDR-capable display, all content, HDR or SDR, would be naturally displayed at the full 10k nits or whatever the actual number is. This is obviously not how things work in practice: OSes and/or displays really want a signal as to whether the full HDR luminance is actually desired. (This reminds me of an earlier HN thread where people complained about HDR video forcing up the brightness on Apple devices.)
- PQ (but not HLG) specifies everything in terms of absolute luminance, but this gets confusing when people want to adjust their display brightness and have everything work relatively in practice.
- Due to lack of support for "overrange" behavior [1], 1D LUTs + matrices are insufficient for representing PQ at all, so you need a 3D LUT just to approximate it. This needs ICCv4, since ICCv2 only supports 3D LUTs for non-display profiles.
- But 3D LUTs are big and fat, and can only give a few bits of accuracy across some parts of the full HDR range. (It seems like there's no form of delta compression?) Most people really hate this. iccMAX can allegedly use 3D parametric formulas, but literally no one implements it since it has a million bells and whistles.
- More importantly, GPUs especially hate big fat LUTs, and everyone uses GPU rendering. In the worst case, some implementations will do everything they can to ignore LUTs in ICC profiles, and instead try to guesstimate some simple-gamma or linear-gamma approximation, which won't end well.
So it does seem to be a combination of "the HDR stack is a mess and needs its own special signaling" and practical concerns about avoiding overly huge profiles.
[0] https://lists.w3.org/Archives/Public/public-colorweb/2017May...
[1] https://lists.w3.org/Archives/Public/public-colorweb/2017May...
That’s precisely what makes it unsuitable for HDR. With PQ, (1, 1, 1) means 10 000 cd/m² – if you simply create an ICC profile with the PQ transfer function, an image that looks right on a hypothetical 10 000 cd/m² monitor will look way too dim when naïvely scaled down (as ICC-type colour management would have you do) to the 300 cd/m² of a typical monitor. HLG, meanwhile, has a transfer function that depends on the peak luminance, which is not possible to do with ICC (the profile would have to assume a specific peak luminance), and the reason that it does that is to preserve the subjective perception of the image.
So, sure, you can prepare an HDR image so that it looks right on a monitor with a 1000 cd/m² peak luminance, describe the colorspace in relative terms using an ICC profile, and you will have “done HDR using ICC”, but that’s arguably a very low bar for “supporting HDR”.
> Many of the programs you use already support the new PNG spec: ... Photoshop, ...
Photoshop does NOT support APNGs. The PR calls out APNg recognition as the 2nd bullet point of "What's new?"
Am I missing something? Seems like a pretty big mistake. I was excited that an art tool with some marketshare finally supported it.
This worries me. Because presumably, changing the compression algorithm will break backwards compatibility, which means we'll start to see "png" files that aren't actually png files.
It'll be like USB-C but for images.
That being said, they also can do dumb things however, right at the end of the sentence you quote they say:
> we want to make sure we do it right.
So there's hope.
That's just changing an implementation detail of the encoder, and you don't need spec changes for that e.g. there are PNG compressors which support zopfli for extra gains on the DEFLATE (at a non-insignificant cost). This is transparent to the client as the output is still just a DEFLATE stream.
[1] https://github.com/w3c/png/issues/39#issuecomment-2674690324
Now, PNG datatype for AmigaOS will need upgrading.
It could be horrible in principle, but actually isn't.
https://svgees.us/blog/img/revoy-cICP-bt.2020.png uses the new colour space. If your software and monitor can handle it, you see better colour than I, otherwise, you see what I see.
The PNG format is specifically designed to allow software to read the parts they can understand and to leave the parts they cannot. Having an extensible format and electing never to extend it seems pointless.
Yeah, we know. That's terrible.
This proves OP analogy regarding USB-C. Having PNG as some generic container for lossless bitmap compression means fragmentation in libraries, hardware support, etc. The reason being that if the container starts to support too many formats, implementations will start restricting to only the subsets the implementers care about.
For instance, almost nobody fully implements MPEG-4 Part 3; the standard includes dozens of distinct codecs. Most software only targets a few profiles of AAC (specifically, the LC and HE profiles), and MPEG-1 Layer 3 audio. Next to no software bothers with e.g. ALS, TwinVQ, or anything else in the specification. Even libavcodec, if I recall correctly, does not implement encoders for MPEG-4 Part 3 formats like TwinVQ. GP's fear is exactly this -- that PNG ends up as a standard too large to fully implement and people have to manually check which subsets are implemented (or used at all).
Same is also true for the most advanced codecs. MPEG-* family and MP3 comes to my mind.
Nothing stops PNG from defining a "set of decoders", and let implementers loose on that spec to develop encoders which generate valid files. Then developers can go to town with their creativity.
Proprietary or open, any visual codec is a battleground. Even in commercial settings, I vaguely remember people saying they prefer the end result of one encoder over another, for the same video/image format, not unlike how photographers judge cameras by their colors.
So maybe, this flexibility to PNG will enable or encourage people to write better or at least unorthodox encoders which can be decoded by standard compliant ones.
Regarding the potential for fragmentation of the png ecosystem the alternative is a new file format which has all the same support issues. Every time you author something you make a choice between legacy support and using new features.
From a developer perspective, adding support for a new compression type is likely to be much easier than implementing logic for an entirely new format. It's also less surface area for bugs. In terms of libraries, support added to a dependency propagates to all consumers with zero additional effort. Meanwhile adding a new library for a new format is linear effort with respect to the number of programs.
Not Sure what youre talking abouz.
If you want to check yours: mediainfo **/*.mp4 | grep -A 2 '^Audio' | grep Format | sort | uniq -c
https://en.wikipedia.org/wiki/TwinVQ#TwinVQ_in_MPEG-4 tells the story of TwinVQ in MPEG-4.
And now think of the younger generation that has grown up with smartphones and have been trained to not even know what a file is. I remember this story about senior high school students failing their school tests during covid because the school software didn't support heif files and they were changing the file extension to jpg to attempt to convert them.
I have no trust the software ecosystem will adapt. For instance the standard libraries of the .net framework are fossilised in the world of multimedia as of 2008-ish. Don't believe heif is even supported to this day. So that's a whole bunch of code which, unless the developers create workarounds, will never support a newer png format.
But that's typical for file extensions. Consider EXE – it is probably an executable, but an executable for what? Most commonly Windows – but which Windows version will this EXE run on? Maybe this EXE only works on Windows 11, and you are still running Windows 10. Or maybe you are running x86-64 Windows, but this EXE is actually for ARM or MIPS or Alpha. Or maybe it is for some other platform which uses that extension for executable files – such as DOS, OS/2, 16-bit Windows, Windows CE, OpenVMS, TOPS-10, TOPS-20, RSX-11...
.html, .js, .css – suggest to use a web browser, but don't tell you whether they'll work with any particular one. Maybe they use the latest features but you use an old web browser which doesn't support them. Maybe they require deprecated proprietary extensions and so only work on some really old browser. Maybe this HTML page only works on Internet Explorer. Maybe instead of UTF-8 it is in some obscure legacy character set which your browser doesn't support.
.zip – supports extensible compression and encryption methods, your unzip utility might not support the methods used to compress/encrypt this particular zip file. This is actually normal for very old ZIP files (from the 1980s) – early versions of PKZIP used various deprecated compression mechanisms, which few contemporary unzip utilities support. The format was extended to 64-bit without changing the extension, there's still a lot of 32-bit only implementations out there. ZIP also supports platform-specific file attributes–e.g. PKZIP for z/OS creates ZIP files which contain metadata about mainframe data storage formats, unzip on another platform is going to have no idea what it means, but the metadata is actually essential to interpreting the data correctly (e.g. if RECFM=V you need to parse the RDWs, if RECFM=F there won't be any)
.xml - okay, it is XML – but that tells you nothing about the actual schema. Maybe you were expecting this xml file to contain historical stock prices, but instead it is DocBook XML containing product documentation, and your market data viewer app chokes on it. Or maybe it really is historical stock prices, but you are using an old version of the app which doesn't support the new schema, so you can't view it. Or maybe someone generated it on a mainframe, but due to a misconfiguration the file came out in EBCDIC instead of ASCII, and your app doesn't know how to read EBCDIC, yet the mainframe version of the same app reads it fine...
.doc - people assume it is legacy (pre-XML) Microsoft Word: every version of which changed the file format, old versions can't read files created with newer versions correctly or at all, conversely recent versions have dropped support for files created in older versions, e.g. current Office versions can't read DOC files created with Word for DOS any more... but back in the 1980s a lot of people used that extension for plain text files which contained documentation. And it was also used by incompatible proprietary word processors (e.g. IBM DisplayWrite) and also desktop publishing packages (e.g. FrameMaker, Interleaf)
.xmi – I've seen this extension used for both XML Model Interchange (XML-based standard for exchanging UML diagrams) and XMIT (IBM mainframe file archive format). Because extensions aren't guaranteed to be unique, many incompatible file formats share the same extension
.com - is it an MS-DOS program, or is it DCL (Digital Command Language)?
.pic - probably some obscure image format, but there are dozens of possibilities
.img – could be either a disk image or a visual image, either way dozens of incompatible formats which use that extension
.db – nowadays most likely SQLite, but a number of completely incompatible database engines have also used this extension. And even if it is SQLite, maybe your version of SQLite is too old to read this file because it uses some features only found in newer versions. And even if SQLite can read it, maybe it has the wrong schema for your app, or maybe a newer version of the same schema which your old version that app doesn't support, or an old version of the schema which the current version of the app has dropped support for...
Has anyone ever used .exe for anything other than Windows?
Under Windows 95/98/Me, most command line tools were MS-DOS executables. Their support for 32-bit Windows console apps was very poor, to the extent that the input and output of such apps was proxied through a 16-bit MS-DOS executable, conagent.exe
First time in my life I ever used GNU Emacs, it was an OS/2 exe. That's also true for bash, ls, cat, gcc, man, less, etc... EMX was my gateway drug to Slackware
Did you know that Microsoft Windows originally ran on top of the much older MS-DOS, which used EXE files as one of its two executable formats? Most Windows users had lots and lots of EXE files which were not Windows executables, but instead DOS executables. And then came Windows 95, which introduced 32-bit Windows executables, but kept the same file extension as 16-bit Windows executables and 16-bit DOS executables.
If you've created an extensible file format, but you never need to extend it, you've done everything right, I'd say.
That's what I would call really extensible, but then there may be no limits and hacking/viruses could have easily a field day.
Will sooner or later be used to implement RCEs. Even if you could do a restriction as is done for eBPF, that code still has to execute.
Best would be not to extend it.
So then it was pointless for PNG to be extensible? Not sure what your argument is.
In an ideal world, yes. In practice however, if some field doesn't change often, then software will start to assume that it never changes, and break when it does.
TLS has learned this the hard way when they discovered that huge numbers of existing web servers have TLS version intolerance. So now TLS 1.2 is forever enshrined in the ClientHello.
And considering we already have plenty of more advanced competing lossless formats, I really don't see why "feed a BMP to deflate" needs a new, incompatible spin in 2025.
Other than JXL which still has somewhat spotty support in older software? TIFF comes to mind but AFAIK its size tends to be worse than PNG. Edit: Oh right OpenEXR as well. How widespread is support for that in common end user image viewer software though?
More generally, PNG has a simple feature to specify what's needed. A file consists of a number of chunks, and one bit in the chunk specifies whether that chunk is required for display. All of the extensions I've seen in the past decades set that bit to "optional".
For example, this update includes a chunk containing EXIF data. As you'd expect, the exif chunk sets that bit to "optional".
https://pico-8.fandom.com/wiki/P8PNGFileFormat
Actual cases of proprietary chunks include iDOT from Apple (apparently a performance optimization for plain images)
https://www.hackerfactor.com/blog/index.php?/archives/895-Co...
and the Macromedia Fireworks save files
https://stackoverflow.com/questions/4242402/the-fireworks-pn...
EG your GPU and monitor both have a USB-C port. Plug them together with the right USB cable and you'll get images displayed. Plug them together with the wrong USB cable and you won't.
USB 3 didn't have this issue - every cable worked with every port.
I believe the problem here is that you will have PNG images that “look” like you can open them but can’t.
If PNG gets extended, it's entirely plausible that someone will view a PNG in their browser, save it, and then not be able to open the file they just saved.
There are those who claim "backwards compatibility" doesn't cover "how you use it" - but roughly none of the people who now have to deal with broken software care about such semantic arguments. It used to work, and now it doesn't.
Do they mention which C libraries use this spec?
USB-C spec is anything but breaking backward compatible.
It's a dichotomy. Either the provider accommodates users with older software or not. The file extension or internal headers don't change that reality.
Another example, new versions of PDF can adopt all the bells and whistles in the world but I will still be saving anything intended to be long lived as 1/a which means I don't get to use any of those features.
This is just pretending that if you have a cat and a dog in two bags and you call it “a bag”, it’s one and the same thing…
Labelling is a poor band-aid on the root problem - consumer cables which look identical and fit identically should work wherever they fit.
There should never have been a power-only spec for USB-C socket dimensions.
If a cable supports both power and data, it must fit in all sockets. If a cable supports only power it must not fit into a power and data socket. If a cable supports only data, it should not fit into a power and data socket.
It is possible to have designed the sockets under these constraints, with the caveat that they only go in one way. I feel that that would have been a better trade-off. Making them reversible means that you cannot have a design which enforces cable type.
Well, yes.
Why can't you use a power+data cable for the vape (or whichever appliance takes both)? What's the deal-breaker here?
The alternative is labeling, or plugging cables in to see if they do what you want them to do.
Both are a poor user interface.
That's even more confusing than the current state of affairs. If my phone has power and data socket, then I cannot use power only cable to only charge it? Presumably with the charger that has power only socket. So I need a cable with two different ends anyway. Just go micro-USB at this point :)
Funnily enough, there is a 100% overkill way to solve such issues. Just use super expensive certified TB cables. Well... plus a A-to-C adapter for noncompliant devices, I guess.
What was broken was the promise of a "single cable to rule them all", partly due to manufacturers ignoring the requirements of USB-C (missing resistors or PD chips to negotiate voltages, requiring workarounds with A-to-C adapters), and a myriad of optional stuff, that might be supported or not, without a clear way to indicate it.
You don't follow spec, you're on your own.
> Many of the programs you use already support the new PNG spec: Chrome, Safari, Firefox, iOS/macOS, Photoshop, DaVinci Resolve, Avid Media Composer...
It might be too late to rename png to .png4 or something. It sounds like we're using the new png standard already in a lot of our software.
The main use case for PNG is web browsers and all of them seem to be on board. Using old web browsers is a bad idea. You do get these relics showing up using some old version of internet explorer. But some images not rendering is the least of their problems. The main challenge is actually going to be updating graphics tools to export the new files. And teaching people that sRGB maybe isn't good enough any more. That's going to be hard since most people have no clue about color spaces.
Anyway, that gives everybody plenty of time to upgrade. By the time this stuff is widely used, it will be widely supported. So, you kind of get forward compatibility that way. Your browser already supports the new format. Your image editor probably doesn't.
This is news to me. I'm pretty sure the main use case for PNG is lossless transparent graphics.
There are about 3.6 billion people surfing the web and experiencing PNGs. That use case, consuming PNGs, seems to dwarf the perhaps 100 million (somewhat wild guess) graphic designers, web developers, and photo editing professionals who manipulate images for publishing (in any medium) or archiving.
If, on the other hand, you're considering the use cases envisioned by PNG's creators, or the use cases that interest the people processing or publishing images, yes, these people are focused on format itself and its capabilities.
I suspect this particular use of "use case" isn't terribly clear. Also these two considerations are not incompatible.
It's not, most images you encounter on the web need better compression.
The main PNG use case is to store lossless images locally as master copies that are then compressed or in workflows where you intend to edit and change them where compressed formats would degrade the more they were edited.
Also if you forbid evolving existing formats, the only alternative to improve is to introduce a new format, and I argue that it would be causing even more fragmentation and be more difficult to adopt to. Look at all the drama surrounding JPEG XL.
I’m not saying this is what will happen — but if I was able to construct a plausible approach to compression in ten minutes, then perhaps it’s a bit early to predict the doom of compatibility.
The first bit of our research is "What can we already make use of which requires no spec update? There are plenty of PNG optimizers. How much of that should go into the typical PNG libraries?"
Same with parallel encoding & decoding. An older image viewer will be able to decode it on one thread without ever knowing parallel decoding was an option.
Here's the worry-a-little part: Everybody immediately jumps to file size as to what image compression is better or worse. That isn't the best take, but it is what it is. So there is pressure to adopt newer technologies.
We often do have a way to maintain some degree of backwards compatibility even when we do this. For example, we can store a downsampled image for old viewers. Then extra, new chunks will know "Mix that with this full scale data, using a different compression".
As you can imagine, this mixing complicates things. It might not be the best option. Sooooo we're researching it :)
Back then, there were no libraries in C# for it, but it's actually quite easy to make APNG from PNGs directly by writing chunks with correct headers, no encoders needed (assuming PNGs are already encoded as input).
https://github.com/NightElfik/Malsys/blob/master/src/Malsys....
While I welcome that there is now PNG with animations, I am less impressed about how Mozilla chose to push for it.
Using PNG's magic numbers and pretend to existing software that it is just normal PNG? That is the same mindset that lead to HTML becoming tag soup. After all, HTML with a <blink> tag is still HTML, no?
I think they could have achieved animated PNG standardization much faster with a more humble and careful approach.
> PNG is pronounced “ping”
See the end of Section 1 [0]
[1] https://edition.cnn.com/2013/05/22/tech/web/pronounce-gif
People believed me. Still funny.
Not sure I'll bother to reprogram myself from “png”, “pung”, or “pee-enn-gee”.
So why can’t you do that with GIF or PNG? People that create things get to name them.
You'll commonly call someone by their pronounced name out of respect, forced or given.
In a situation where someone does something really stupid or annoying and the forced respect isn't there, most people don't.
And if they pick something dumb enough other people get to ignore them.
But also, no, not universally even for babies, especially when the name is something ridiculous like X Æ A-Xii where even parents disagree on pronunciation, or when the person himself uses a "non-specced" variant
On inanimate objects: Aluminium was first ratified by the IUPAC as aluminium⁰, with the agreement of its discoverer Sir Humphrey Davy¹, yet one huge nation calls it something else…
On people: nicknames are a thing, are you saying those are universally wrong? But yes, when a person tells me that they'd prefer their name pronounced a different way, or that they'd prefer a different name entirely, or that they don't like the nickname other use for them, you can bet your arse that I'll make the effort to use their preferred name+pronunciation in future.
------
[0] Though it should be noted that aluminum was, a few years after, officially accepted as an alternate form.
[1] He initially called it aluminum in the first paper.
Hard-g is wrong, and those who use it are showing they have zero respect for others when they don't have to.
It's the tech equivalent to the shopping cart problem. What do you do when there is no incentive one way or the other? Do you do the right thing, or do you disrespect others?
Naming is probably one of the few language areas that I think should be prescriptive, even while language at large is descriptive.
A file format is not a sentient being. The creator's intent matters much more. If GIF had sentience and could voice a desire one way or the other, the whole discussion would be moot as it would clearly be disrespectful to intentionally mispronounce the name.
The G in gif is for graphics. Not 'giraffics'. And most people in the world have no idea what Jif even is, much less a particular catchphrase from an old ad campaign that barely even connects.
English has both pronunciations for "gi" based on origin. Giraffe, giant, ginger, etc from Latin; gift, give, (and presumably others) from Germanic roots.
Using the preferred one is just a matter of politeness.
Also, it's quite ironic to prescribe "linguistic prescriptivism" as wrong.
https://file.org/extension/jif
https://fileinfo.com/extension/jiff
https://www.reddit.com/r/todayilearned/comments/4rirr8/til_t...
Wrt/ communication, aside from personal preference, one can either respect the creator, or the audience. If I stand in front of 10 colleagues, 10 out of them would not understand jif, or would only get it because this issue has some history now. gif on the other hand has no friction.
Ghengis Khan for example sounds very different from its original Mongolian pronunciation. And there is a myriad others as well.
I continue to pronounce it how I prefer it, not as a slight, but most people here would be surprised by the soft g.
If I ever meet him I’ll attempt to pronounce it soft-g.
On the other hand, even though my name exists and is reasonably common in English, I’m fairly certain neither you or the GIF creator would address me the way I pronounce my name. I would understand anyway, and wouldn’t care one bit.
The debate itself is old. "Since the 90s" Wikipedia says, and keep in mind the format was is from 1987 - so I would say the debate is on from the get-go. Appropriate, too, if you think back, arguing about this kind of stuff was pretty common. Emacs vs vim, browser wars, different kinds of computers, tribalism everywhere.
Thinking about it, I think I understand why hard G makes sense for people. With GPU, we pronounce the the individual letters, as it's clearly an abbreviation - as no sane English word starts with "gp". With GIF though, even though it's an abbreviation, it looks a lot like a normal word, "gift", and English also has "give", another one with a hard G, so it feels familiar to say. Moreover, the US, where GIF comes from, has Jif already established as a peanut butter brand, so it makes sense to not pronounce a newly invented, differently written word the same as an already established thing. Well, at least to some it makes sense!
Surely they aren't releasing a new, incompatible version and expecting us to pretend it's the same format...?
> This updates the existing image/png Internet Media type
whyyyyyyy
We went to pretty extreme lengths to make sure old software worked with the new changes. Effectively, the limit will be the software, not the image.
For example, you can imagine some old software that is unaware of color spaces and treats everything as sRGB. There is nothing we can do to make that software show a Display P3 correctly. However, we can still show the image well enough that a user understands "that is a red apple".
Society doesn't need a new image format. I'd wager to say not any new multimedia format. Big corporate entites do, and have churning them out at a steady pace.
Look at poor webp - a format pushed by the largest industry players - and the abysmal everyday use it gets, and the hate it generates.
Estimates are that 95% of Internet users have a browser that supports WebP and that ~25% of the top million websites serve WebP images. I wouldn't call that abysmal.
Edit: and good luck uploading the format to the majority of webforms that aren’t faang.
Interns won't want to work on a dead end like this. Moreso they need to be supervised by someone that doesn't want to get removed by being the lowest X% usefulness in a company. So all these existing tools that aren't primary revenue generators just sit on coast mode.
Let’s also not forget the dependency mess that leaves in applications before we do though..
Better image formats serve entities who store images at scale, not end users.
In what other industry would it be considered acceptable to exclude 5% of visitors/users/clients?
Note that I'm looking at "all tracked," which excludes 2% "other" browsers in the data whose featureset is not known.
That's not how it works.
The server declares what versions of media it has, and the client requests a supported media format. The same trick have been used for audio and video for ages too.
Example:
<picture>
<source srcset="a.webp" type="image/webp">
<img src="fallback.jpg">
</picture>Will say though that it's not universal, it depends heavily on the corner of the internet you're on.
But even beyond that, most file formats have a bit of a header at the start of the file that declares the actual format of the file. Browsers already can understand that and use the correct render for a file without an extension.
Images are often at different resolutions too, that way, depending on the pixel density of the device, and the physical size, the browser can select the photo that has high enough resolution, but not one that is needlessly large, while also selecting the preferred image format.
See CSS image-set : https://developer.mozilla.org/en-US/docs/Web/CSS/image/image...
Rational, or economical? I find it rational to help someone in need since I'd want others to do the same to me, even if it's not financially profitable for me. Imo more factors flow into what's rational, but I understand what you mean by corporate greed working this way (less than 10% of people are blind, neither male nor female, run a free operating system or can't afford a new computer, etc., so yep they're not profitable groups and for-profits don't optimise for that)
If a corporation has determined that profit maximization is their core tenet, excluding the needs of a minority of users can likely be deduced in a rational manner from that tenet. That is precisely why values need to be forced onto corporate actors through regulation, e.g. in this case through mandatory accessibility guidelines like EU directive 2019/882 that enters into force this very week.
Or Linux users? Or even Firefox users in our market?
As for Linux users… I do recall they were even less than the 3%. Firefox users were more tho.
In any case, I’m almost sure most Linux users were fine. We just didn’t wanted to support old browsers.
e.g. cars - not everyone is physically able to drive books - blind people can't read music - deaf people can't hear
It is a form of 80/20 or 90/10 rule the last small percentage costs as much as the majority.
(Also, the parent comment's example is also not so good because as someone else pointed just because the top 25% websites are serving webp it does mean they're not serving alternative formats for those who does not support it, as this is quite trivial to setup)
One example is Sony's SRF camera raw format.
Programs like Photoshop and Affinity have to bring their own decoders where previously none were required.
Having ask that in a slightly confrontational way, one of the reasons I started using VLC all those years ago, and still use it to this day, was having trouble with other media players that relied on OS support fail to work well (or at all) with some codecs, while VLC brought support for them, and their dog, built-in and reliable. Dragging your own format support libraries with you can be beneficial.
It doesn't matter if the alternative is technically superior once the majority use the mainstream thing.
There are so many uneven areas of Reddit where WebP doesn't work. Old reddit, profile support, mod tools, etc.
My webcrawler sucks down a lot of WebP images, at least it did before it got the smackdown from Cloudflare.
Hell, for some software features (like stickers in some chat apps), WebP is mandatory.
HEIFF files, on the other hand...
We used to do this with JPEG, in fact. And that's why many pictures on Facebook from pre-2018 or so all have a distinctive grainy look. It's artifacts on top of artifacts. Storage on phones isn't tight anymore, we don't need to store photos in a format meant to minimize bytes at the expense of quality.
Photoshop still won’t open it, MacOS preview opens it but then demands to convert it to tiff when you try to edit it
> Many […] programs […] already support the new PNG spec: Chrome, Safari, Firefox, iOS/macOS, Photoshop, DaVinci Resolve, Avid Media Composer...
> Plus, you saw some broadcast companies in that list above. Behind the scenes, hardware and tooling are being updated to support the new PNG spec.
Whilst we're at it, please get rid of RGB and make it N channels too.
Libraries can choose to render that into a 3 channel, 8 bit buffer for legacy applications - but the data will be there for CMYK or HDR, or depth maps, or transparency, or focus stacking, or any other future feature!
They say it's technically compatible since older image decoders should recognize the PNG file is using a different compression algorithm than the default.
> Many programs already support the new PNG spec: Chrome, Safari, Firefox, iOS/macOS, Photoshop, DaVinci Resolve, Avid Media Composer...
This is intentionally ignoring the fact that there are countless PNG decoders out in the wild, many using libpng the standard decoder last updated 6 years ago; and they will not be able to read the new PNG v2 files.
They should have used a different file extension, PNG2, to distinguish this incompatible format. Otherwise, users will be confused why their newly saved PNG file cannot be read by certain existing programs.
There's a PR for APNG: https://github.com/pnggroup/libpng/pull/706 – it seems there was some work for HDR in e.g. https://github.com/pnggroup/libpng/pull/635 as well. Related: https://github.com/pnggroup/libpng/issues/507
https://www.libpng.org/pub/png/libpng.html
Looks like this is the proper location for the project.
You'll never be able to faithfully represent an HDR image on a non-HDR system, but you'll still see an image.
What about it?
"Lossless WebP is typically 26% smaller than PNG, while lossy WebP can be 25-34% smaller than JPEG at equivalent quality levels"
This literally saves houndred of thousand of cost, bandwith, electricity every month on the internet. In fact, I strongly belive that this is one of the greatest contributions from Google to society just like ZSTD from Facebook.
"WebP is used by 16.7% of all websites. This means that while it's a popular image format, it's not yet the dominant format, with JPEG still holding the majority share at 73.0%, according to W3Techs. However, WebP offers significant advantages in terms of compression and file size, making it a preferred choice for many web developers. "
¯\_(ツ)_/¯
Therein lies the lie.
Image and video compression comparisons are like statistics with the right corpus and evaluation criteria you can should whatever narrative you want to push.
We need good video formats however. Video makes up most of the global internet traffic, probably accounts for a good part of global storage capacity too. Even slightly better compression will have a massive impact.
We jumped through quite a lot of hoops to make sure old software will be able to display new images. They simply won't display them optimally. But for the most part, that would be because the old software wouldn't display images optimally anyway. So the limit was the software, not the format.
What I mean by this is old software that treats everything as sRGB wouldn't correctly show a Display P3 image anyway. But we made sure it will still display the image as correctly as it could.
But you can absolutely have an SDR image encoded using a large color space. So I am not sure why the author talks about color primaries when it tries to justify HDR… I still don’t know what kind of HDR images this new PNG variant can encode.
In this case there could be an embedded reduced colour space image next to an extended color space one
There is also some leeway for how encoding is done as long as you end up with a valid stream of bits at the end (called the bit stream format), so encoders can improve over time. This is common in video formats. I don’t know if a lossless image format would benefit much from that.
PNG is a highly structured file format internally. It borrows design ideas from formats like EA's Interchange File Format in that it contains lists of chunks with fixed headers encoding chunk type amd length. Decoders are expected to parse them and ignore chunk types they do not support.
Lossless AVIF is not competitive.
However, lossless WEBP does not support indexed color images. If you need palettes, you're stuck with PNG for now.
And buffer sizes aren't handled in a good way. You have to provide pre-allocated memory, guessing how big it is supposed to be. Then you get a "not big enough" error. This is a guessing game, not a good design. You're forced to overshoot, then shrink the buffer afterwards.
---
In different APIs, there tends to be a function you call to get the required buffer size. For example, many Win32 API functions make you call them with a buffer size of 0, then you get the actual required size back. Another possibility is having the library allocate the memory, and return the allocated buffer to you. Since cross-module memory management is hairy (different `malloc` implementations can't interoperate), some APIs let you provide the `malloc`, `realloc`, and `free` functions.
I designed the article to be accessible and understandable for the average person. So I took some liberties like showing only HDR primaries and not deep diving into HDR transfer functions. People understand the primaries intuitively.
But you are right that a wide color image could also use those same primaries without being HDR.
My goal was to be as truthful as possible while still being digestible at a glance.
In the article, I linked to Chris Lilley's post which explains it more thoroughly for the technical people.
After 20 years of success, we can't resist the temptation to mess with what works.
It has, but WWW is still de facto sRGB, and will be for a long time still. But again, I'm not strictly opposed to evolving PNG, I just hope they don't ruin it in the process, because that's usually what happens when something gets update for a modern audience. I'll be watching with mixed optimism and concern.
The continued popularity of non-HDR 1080p screens on laptops is a bleak reminder that most people would rather save a couple hundred bucks than buy HDR capable hardware.
HDR is great for TVs and a nice-to-have on phones (who mostly get it for free because OLEDs are the norm these days), but display technology only advances as much as its availability in low-cost devices.
Not sure how HDR encoding works, but my impression is that you can set a nominal white point other than (1, 1, 1) in your specified colorspace. This is an extension, but orthogonal to specifying the colorspace itself and the gamut.
But wide color gamut was already possibly in PNG via ICC profiles (HDR was not). And those primaries I showed could have been used in a wide color image.
So the image is a bit misleading or red-flag-y to experts who know. But to the average person, I think it is as truthful as I can be without getting too deep in the weeds.
For example 16bit (integer) TIFF files 'with headroom', i.e. where some bits were used to represent data over 1.0 (HDR) was a common approach for VFX work in the 90's.
16bit float TIFF is also thing since 33 years. Adobe DNG is modeled after TIFF. High end offline renderers have traditionally been using TIFF (with mip-maps) to store textures.
TIFF supports tags so primaries and white point or a known color space name can be stored in the file.
The format is so versatile, it is used everywhere.
And of course it also supports indexed color, i.e. a non-negotiable feature at the time PNG was introduced.
PNG was meant to replace GIF. Instead of looking what was already there some group of "experts" and "enthusiasts" (quote Wikipedia) succumbed to their NIH complexes. If licensing/patent woes over compression algorithms had been a motivator, why not just add a new one to TIFF?
The fact that PNG stores straight/unpremultiplied alpha says everything if you know anything about imaging in computer graphics.
And the fact that the updated format spec just released didn't address this tells you everything you need to know about the group in charge of that, today.
PNG is the VHS of image formats. It should have never seen the light day of in the first place nor the adoption it did.
Yeah, I love the fact that you can embed a PDF file inside a TIFF.
> And the fact that the updated format spec just released didn't address this tells you everything you need to know about the group in charge of that, today.
What does it say? That they are naive or have the wrong priorities? Their rationale for this seems quite reasonable to me: https://www.w3.org/TR/PNG-Rationale.html#R.Non-premultiplied...
E.g. an associated pixel with the 8bit/channel RGBA value 255, 0, 0, 0 (glowing red).
Because PNG can only store associated data a reader must associate before displaying. And that will give you a value of 0, 0, 0 after (black instead of additive red). See e.g. [1] why this matters.
Additionally the PNG spec does not specify if the alpha is linear. Some PNG readers/writer assume it is, some assume it has gone through/should go through an sRGB transfer curve instead. It mostly works until it doesn't.
The fact that the spec. doesn't specify which one it should be is another telltale sign that it was written by people unaware of the subtleties of image processing.
I understand that unassociated alpha gives you more precision in 8bit and since people wanted to e.g. store color ramps (with alpga) in PNG at the time (pre-SVG) and most image processing software (i.e. mainly Photoshop then) would not dither gradients for 8bit, this really mattered.
But it's 2025. And when 16bit PNG got introduced this should have definitely had associated (and explicitly linear) alpha.
[1] https://academysoftwarefdn.slack.com/archives/C05782U3806/p1...
Quote the relevant section, Slack requires a log-in.
> Additionally the PNG spec does not specify if the alpha is linear.
Section 12.1 of the PNG spec seems to specify exactly that: “gamma does not apply to alpha samples; alpha is always represented linearly.”
They do not mention precision at all in their rationale for that: “We standardized on non-premultiplied alpha as being the lossless and more general case.”
> And when 16bit PNG got introduced...
PNG has supported 16-bits per component since it was first introduced (see version 1.0 of the spec or RFC 2083).
How is this "more general"? Unpremultiplied is actually lossy (not so as far as precision goes but critically so if you talk about meaning/information).
> PNG has supported 16-bits per component since it was first introduced (see version 1.0 of the spec or RFC 2083).
True, my bad. But there have been many updates to the spec over the years.
I btw found a mention of alpha to be assumed to be linear in [1] but in a comment in a sample code snippet.
Quote:
/*
* Compositing is necessary.
* Get floating-point alpha and its complement.
* Note: alpha is always linear; gamma does not
* affect it.
*/
On the note of alpha: [2] is a good piece to read to understand why this matters, specifically the section "PNG cannot store all clamped linear values…".
[1] https://www.w3.org/TR/PNG-Encoders.html#E.Alpha-channel-crea...
[2] https://www.realtimerendering.com/blog/png-srgb-cutoutdecal-...
How can you call this basic fail a success?
Pleasantly surprised.
I did skim through the specs, it seems most of it is related to cleanup and optional blocks, so it seems PNG is still safe, am I wrong? (asking those who did dive into the new specs deeply).
Is this written exactly for (1) people who implement/maintain this and, I say this with love, (2) nerds. Or will there be effects outside of a microscopic improvement on storage + latency.
PNG was a huge deal when it was new, mostly because of all the headaches Unisys was giving everyone over GIF compression patents. This new standard is mostly of interest to people that have reason to care about what format their image data is in.
PNG is popular with some Commercial Application developers, but the exposure and color problems still look 1980's awful in some use-cases.
Even after spending a few grand on seats for a project, one still gets arrogant 3D clown-ware vendors telling people how they should run their pipeline with PNG hot garbage as input.
People should choose EXR more often, and pick a consistent color standard. PNG does not need yet another awful encoding option. =3
A very basic rec.709 workflow tutorial:
https://www.youtube.com/watch?v=lf8COHAgHJs
The Andreas Dürr LUT pack:
https://www.youtube.com/watch?v=dDKK54CeXgM
https://cinematiccookie.gumroad.com/l/bseftb?layout=profile
The calibration workflows also depend heavily on what is being rendered, source application(s), and the desired content look. There were some common free packs on github for popular programs at one time. Should still be around someplace... good luck. =3
What are you talking about? It's a bitmap. It has nothing to do with "exposure and color problems."
If you've never encountered the use-case, than don't worry about the aesthetics. Seriously, many vendors also just don't care... especially after they already were paid. Best of luck =3
I think your experience is with some tool that made bad PNGs. That is a problem with the tool, not the format.
Have a look at a tutorial that dives into the basic details, and consider learning something:
https://www.youtube.com/watch?v=pLt1230dtYE
https://www.youtube.com/watch?v=mb0b83MML78
https://www.youtube.com/watch?v=egtnkhuUe_E
PNG has its use-cases, and some people do expect that baked color-space garbage look given it dominates a lot of low-end media. Have a great day =3
In the first video, the person loads the image and manually chooses a gamma transfer function with 2.2. If that was then saved, it would produce the washed-out fireball you mentioned.
In the second video, the person loads the image and manually chooses rec.709, which is also gamma tf and also produces washed-out fireball. In fact, the EXR image he loads literally has a bright fireball and you see it get washed out.
If you want to make claims about EXR being better than PNG, you need to say why storing the values as floating point is better than integer. But the blown-out fireball example is just incorrect. As evidence, I'll point to HDR. ANYTHING you see in an HDR movie is now 100% losslessly reproducible in a PNG.
!!!
I'm retired and making zero money here. (I'm actually losing money on it. Wish I had a company sponsoring me for the flights and hotels for meetups.)
All participants are required to not patent any piece of it. We work hard to make sure we only reference open standards. (This one is quite tricky. We have to convince other standard orgs to make their stuff free.)
I could see the argument for getting around a gate. But fwiw I don't think that's the case :)