Running Adobe's 1991 PostScript Interpreter in the Browser

why deflate your own position with this (worthless-untrue-spineless) statement? Which library is doing the work? who writes that library and maintains it?

https://news.ycombinator.com/item?id=41962062

>PostScript is kind of like a cross between Forth and Lisp, but a lot more like Lisp actually. And its data structures, which also represent its code, are essentially s-expressions or JSON (polymorphic dicts, arrays, numbers, booleans, nulls, strings, names (interned strings), operators (internal primitives), etc.)

https://news.ycombinator.com/item?id=21968175

>Kragen is right that PostScript is a lot more like Lisp or Smalltalk than Forth, especially when you use Owen Densmore's object oriented PostScript programming system (which NeWS was based on). PostScript is semantically very different and much higher level that Forth, and syntactically similar to Forth but uses totally different names (exch instead of swap, pop instead of drop, etc).

https://news.ycombinator.com/item?id=21968842

>You're welcome! OOPS (Object Oriented PostScript ;), I meant to say that PostScript and Lisp are homoiconic, but Forth is not. The PSIBER paper on medium goes into that (but doesn't mention the word homoiconic, just describes how PS data structures are PS code, so a data editor is a code editor too).

The Shape of PSIBER Space: PostScript Interactive Bug Eradication Routines — October 1989:

https://donhopkins.medium.com/the-shape-of-psiber-space-octo...

The Story of Sun Microsystems PizzaTool: How I accidentally ordered my first pizza over the internet.

https://donhopkins.medium.com/the-story-of-sun-microsystems-...

PizzaTool Source Code (in object oriented NeWS PostScript using Owen Densmore's "class.ps"):

https://www.donhopkins.com/home/archive/NeWS/pizzatool.txt

NeScheme and Schlumberger's LispScript:

https://donhopkins.com/home/archive/NeWS/NeScheme.txt

>PostScript is often compared to Forth, but what it lacks in relation to Forth is a user-extensible compiler. You can write your own PostScript control structures and whatnot, like case and cond, to which you pass procedures as arguments on the stack, but the PostScript scanner is not smart -- but there is no preprocessing done to the PostScript text being read in, like the way immediate words in Forth can take control and manipulate the contents of the dictionary and stack while the text source is being read in and compiled, or like the way Lisp macros work. This is one of the things I would like to be able to do with something like LispScript.

>"Lisp is the language for people who want everything, and are willing to pay for it." -Russell Brand (the old school Lisp hacker "wuthel" from MIT, not the crazy MAGA rapist)

If you want to efficiently implement a PostScript interpreter with rendering in the web browser (or node), you just have to reach for the canvas 2d rendering context, which is essentially the full PostScript stencil/paint imaging model upgraded to the Porter/Duff compositing model with alpha channels, but without the user defined font rendering and halftoning machinery (which you could implement on top of it).

https://keithp.com/~keithp/porterduff/p253-porter.pdf

PostScript has always had the black and white "image" and "imagemask" operators, but they are clumsy, don't support any kind of image processing, and you have to use "readhexstring" to read hex images, but later versions support color images.

NeWS has "readcanvas" to directly read binary Sun raster files (including color) from files and over the network. It also had memory mapped canvases, which I used for the HyperLook version of SimCity so the C simulator engine could efficiently render the tiles and map views with overlays into memory, and NeWS could scale and render them quickly. I also used memory mapped canvases for my NeWS/HyperLook cellular automata machine, which was implemented in C and scaled and rendered and had a real time painting UI implemented in NeWS PostScript (the client and server took turns "owning" the pixels by ping-ponging messages over the localhost network, so each could draw into the cells in turn, and you could render PostScript directly into the 8-bit color cells for interesting effects, melt people's faces, and clip them on the screen to a window in the shape of a lava lamp).

http://www.art.net/~hopkins/Don/hyperlook/HyperLook-SimCity....

http://www.art.net/~hopkins/Don/art/cam-screen.gif

http://www.art.net/~hopkins/Don/art/RoyalPineAura.gif

The Apple PostScript printer drivers used (and Adobe's Blue Book documented) an indirect but efficient hack that tricked the custom halftone rendering machinery into performing a perfect pattern fill (so you could print MacDraw files, etc).

https://news.ycombinator.com/item?id=22570865

DonHopkins on March 13, 2020 | parent | context | favorite | on: Finding Mona Lisa in the Game of Life

Error diffusion dithering would work very well as initial conditions for many cellular automata rules like Life, especially counting rules (which life is) that stay alive with intermediate numbers of neighbors.

Conway's Life stays alive with 2 or 3 neighbors out of 9, or 2/9 .. 3/9, so gray scales between 22% .. 33% would be the most active.

Halftone screens would have different results, but their regularity might work well with certain CA rules and screens.

PostScript gives you a lot of control over the halftone screen definition.

Halftone screens can use any kind of repeating pattern, there just has to be the proper ratio of white to black pixels to make it look the right brightness. You could even design a set of halftone screen patterns that were precisely matched with a particular cellular automata rule to produce interesting fertile or static patterns. And you can even use any arbitrary pattern for each level, even if they aren't the right brightness, for aesthetic reasons.

The original PostScript LaserWriter was able to efficiently perform pattern fills to print tiled MacDraw images, by defining a custom halftone screen for each tile pixel pattern, that printed precisely the right pixels when you set just the right gray level: the ratio of on pixels to the total number of pixels in the tile. The spot function basically tells the halftone screen machinery what order to turn the dots on as the gray level goes from 1 to 0 (which results is seamless tiling with nearby gray tiles). Take a look at the PostScript header of an old MacDraw file some time to see the really bizarre code that does that by abusing the "setscreen" operator with a contrived spot function. (That was extremely tricky and gave GhostScript problems for years. The trick is documented in Program 15 page 193 of the awesome PostScript "Blue Book", and it uses a lot of memory! It's one of the coolest tricky PostScript hacks I've ever seen!)

https://web.archive.org/web/20210303050038/https://www.adobe...

https://melusine.eu.org/syracuse/postscript/bluebook/?opt=ep...

https://www-cdf.fnal.gov/offline/PostScript/BLUEBOOK.PDF

>This program demonstrates how to fill an area with a bitmap pattern using the POSTSCRIPT halftone screen machinery. The setscreen operator is intended for halftones and a reasonable default screen is provided by each POSTSCRIPT implementation. It can also be used for repeating patterns but the device dependent nature of the setscreen operator can produce different results on different printers. As a solution to this problem the procedure, ‘‘setuserscreen,’’ is defined to provide a device independent interface to the device dependent setscreen operator.

>IMPLEMENTATION NOTE: Creating low frequency screens (below 60 lines per inch in device space) may require a great deal of memory. On printing devices with limited memory, a limitcheck error occurs when storage is exceeded. To avoid this error, it is best to minimize memory use by specifying a repeating pattern that is a multiple of 16 bits wide (in the device x-direction) and a screen angle of zero

https://www.grymoire.com/Postscript/Halftones.html

https://en.wikipedia.org/wiki/Halftone#Digital_halftoning

Here is what happened when I mixed PostScript and cellular automata (and HyperLook, like a PostScript version of HyperCard):

Fun with Cellular Automata [...more at https://news.ycombinator.com/item?id=22570865 and http://www.art.net/~hopkins/Don/art/cell.html ...]

Eh, I'm with Apple on this one: we can just use Ghostscript. Apple's move effectively forces the few applications that need to use PostScript on macOS to migrate from a proprietary PostScript implementation to an OSS one, which strikes me as ultimately a good thing.

https://en.wikipedia.org/wiki/Don_Lancaster

Don Lancaster has died (gilaherald.com)

https://gilaherald.com/obituary-for-don-lancaster/

HN discussion:

https://news.ycombinator.com/item?id=36545595

Woody Baker was one of his biggest fans on comp.lang.postscript!

https://news.ycombinator.com/item?id=36546584

DonHopkins on July 1, 2023 | parent | context | favorite | on: Don Lancaster has died

I have always been a huge fan of Don Lancaster's wizardly writing about PostScript, who not only regularly published in Computer Shopper, but also generously ran a free PostScript help line at his own personal phone number. But Woody Baker was by far his biggest most enthusiastic fan of all (and highly eccentric in personality and coding style), and he would regularly extol and evangelize Don Lancaster's virtues and ideas on comp.lang.postscript. Once around March 4 1990, I gave Woody Baker some feedback on his comp.lang.postscript faq, including the suggesting that he might consider leaving Don Lancaster's personal phone number out of it, but he replied:

>Again, I want to thank you for your contributions. You and D. Cortesi have been most helpful. The two of you gave me very in depth feedback. I have moved almost all the editorializing to the end. I have moved the style stuff to the end. As for DON LANCASTER, I left his phone number in. Don publishes it regularly in the computer shopper, as a free PostScript help line. He is self-employed, and a widely published Author, for TAB books among other things. He says he averages 80 helpline calls a day. He also sells programs and books that he is self publishing. I can assure you, he won't mind at all.

Woody loved to talk in depth about how amazing and inspirational Don Lancaster was, and defend his well deserved honor and reputation whenever anybody criticized his work.

http://computer-programming-forum.com/36-postscript/ff79f7dd... [broken link, not on archive org]

>True. Don lives in an APPLE II world. You are wrong, however in certain statements. He has (unfortunatly) mentioned what FLXPROC does. It happens to be critical to certain things, that several consultants are working on here and there. He knows enough not to blab some things, and jerk work out from under individuals (at least some of the time). Don has dug pretty deeply into certain areas of PS, and I have dug deeply into other areas of PS. Don is first and formost a writer. He's self employed, and extremely intellegent. I am first and formost a software engineer, and secondly a writer. I tend to write, however for clients. I'm confident that I know what FLXPROC does, and what it is good for. And I'm sure Don does also. I more or less told him about FLXPROC and he more or less told me what it does. After first quarter 1990, some things will be essentially worthless as consulting info, and will rapidly become public knowlege. I don't applogize for keeping the lid on some things. I'm a bit of a mercenary in a way. I like consulting.

>Cheers

>Woody

Their great respect was mutual:

https://archive.org/stream/Ask_the_Guru_v1

https://archive.org/stream/Ask_the_Guru_v1/Ask_the_Guru_v1_d...

>Don Lancaster's ASK THE GURU Selected reprints

>Copyright c. 1987 by Don Lancaster and Synergetics, Box 809, Thatcher, AZ 85552. (520) 428-4073

>Electronically self-published using the Apple //e computer and the LaserWriter Plus. All graphics were done in their entirety by ProDOS Applewriter 2.1.

[...]

>I don't think I was ever more amazed when Woody Baker of The Copier Store mailed me back one of my very own laser printed business cards — redone in real ink in an almost "embossed" gold! Turns out Woody had found an older Omnicrom machine scunging around unsold in the back of his warehouse and fired it up. Lo and behold, the instant conversion of any toner image to real ink in stunning colors!

Example 10 of Don Lancaster's Postscript Show & Tell beautifully illustrates how an Omnicrom printer works:

https://www.tinaja.com/glib/psnt.pdf

>Example ten -- What appears hear as a mild-mannered Postscript technical illustration is really the secret of full color laser printing.

>Omnicrom sheets are real ink applied to a carrier. You place the sheet in contact with your toner image and then run it back through the fusion rollers a second time. The ink gets fused over the toner.