I'm personally skeptical about GPU acceleration being the answer to 2D rendering for various reasons.
I'm looking forward to Blend2D < https://blend2d.com/ > which is JIT based maturing and being the preferred solution.
I believe the best way is probably to use Blend2D for rendering glyph bitmaps and then compositing them into the full text on GPU.
Sadly, CPU memory is still plenty slow compared to GPU memory and when you need to copy around 100 MB images (4K RGB float), then that quickly becomes the limiting factor.
At the moment when you render text Blend2D queries each character from the font and then rasterizes all the edges and runs a pipeline to composite them. All these steps are super optimized (there is even a SIMD accelerated TrueType decoder, which I have successfully ported to AArch64 recently), so when you compare this approach against other libraries you still get like 4-5x performance difference in favor of Blend2D, but if you compare this method against cached glyphs Blend2D loses as it has to do much more work per glyph.
So the plan is to use the existing pipeline for glyphs that are larger (let's say 30px+ vertically) and to use caching for glyphs that are smaller, but how it's gonna be cached is currently in research as I don't consider simple glyph caching in a mask a great solution (it cannot be sub-pixel positioned and it cannot be rotated - and if you want that subpixel positioned the cache would have to store each glyph several times).
There is a demo application in blend2d-apps repository that can be used to compare Blend2D text rendering vs Qt, and the caching Qt does is clearly visible in this demo - when the text is smaller Qt renders it differently and characters can "jump" from one pixel to another when the font size is slightly scaled up and down, so Qt glyph caching has its limits and it's not nice when you render animated text, for example. This is a property that I consider very important so that's why I want to design something better than glyph masks that would be simple to calculate on CPU. One additional interesting property of Qt glyph caching is that once you want to render text having a size that was not cached previously, something in Qt takes 5ms to setup, which is insane...
BTW one nice property of Blend2D text rendering is that when you use the multithreaded rendering context the whole text pipeline would run multithreaded as well (all the outline decoding, GSUB/GPOS processing, rasterization, etc...).
You can see some existing benchmarks here:
- https://blend2d.com/performance.html
That's too bad. Is their a successor planned or is Skia the recommended alternative?
If you consider libraries that offer CPU rendering there are basically:
- AGG (CPU only)
- Blend2D (CPU only, GPU planned, but not now)
- Cairo (CPU only)
- Qt's QPainter (CPU only, GPU without anti-aliasing / deprecated)
- Skia (CPU + GPU)
- Tiny Skia (CPU only, not focused on performance)
- GPU only libs (there is many in C++ and Rust)
As an author of Blend2D I hope that it will be a go-to replacement for both AGG and Cairo users. Architecturally, Blend2D should be fine after a 1.0 release as the plan is to offer a stable ABI with 1.0 - And since Blend2D only exports C-API it should be a great choice for users who want to use every cycle and who want their code to work instead of making changes every time the dependency is updated (hello Skia).
At the moment Blend2D focuses on AGG users though, because AGG is much more widespread in commercial applications due to its licensing model and extensibility. However, AGG is really slow especially when rendering to large images (like 4K) so switching from AGG to Blend2D can offer a great performance benefits while avoiding other architectural changes of the application itself.
BTW Blend2D is still under active development. It started as an experiment and historically it only offered great performance on X86 platforms, but that is changing with a new JIT backend, which provides both X86 and AArch64 support and is almost ready for merge. This is good news as it will enable great performance on Apple hardware and also other AArch64 devices, basically covering 99% of the market.
- Canvas Ity (https://github.com/a-e-k/canvas_ity)
It's a tiny single-header C++ library in the style of the STB libraries. My aim was to make it dirt simple to be able to drop into almost any project and get high-quality rendering while providing an API comfortable to those used to <canvas>.
I've been checking out Blend2D every now and then. It seems like a very nice option for the bigger, but faster and more fully-featured end of the spectrum.
(Though for what it's worth, while raw performance isn't my priority, my little library still can hit about 70fps rendering the Postscript Tiger to 733x757 res with a single thread on my 7950x. :-)
BTW for comparison - Blend2D can render SVG tiger in 1.68ms on the same machine (I also have 7950X) so it can provide almost an order of magnitude better performance in this case, which is great I think. But I understand the purpose of your library, sometimes it's nice to have something small :)
NanoVG provided Canvas.Context kind of API in plain C.
AmanithVG is the library on which our SVG renderer: https://www.amanithsvg.com is based. All closed source as now, but things may change in future.
I will do some benchmarks of the current (and next, when the new GPU backend will be ready) version of our libraries against other libraries. Do you know if there are any standard tests (besides the classic post script Tiger)? Maybe we can all agree on a common test set for all vector graphics libs bechmarks?
Regarding benchmarks - I think Tiger is not enough. Tiger is a great benchmark to exercise the rasterizer and stroker, but it doesn't provide enough metrics about anything else. Tt's very important how fast a 2D renderer renders small geometries, be it rectangles or paths. Because when you look at screen most stuff is actually small. That's the main reason why Blend2D benchmarking tool scales the size of geometries from 8x8 to 256x256 pixels to make sure small geometries are rendered fast and covered by benchmarks. When you explore the results you will notice how inefficient other libraries actually are when it comes to this.
https://github.com/thorvg/thorvg#dependencies
AFAIK they have experimental GPU backend but I'm not sure how far they are with it.
I wonder what he’s up to these days?
Update/edit:
Ahh he moved on to Ampere: https://www.linkedin.com/in/carl-worth
Also I was a bad fan: the library had a co-founder too I thought it was a bespoke creation of Carl’s own making.
I remember building a bunch of stuff from source back in the day and a lot of Linux applications had Cairo as a dependency.
> There was an attempt at making Cairo support GPU rendering, which did not work particularly well due to the library being designed around stateful operation based upon the PostScript model—resulting in a convenient and familiar API, great output quality, but hard to retarget and with some particularly slow corner cases. Meanwhile, other web engines have moved more work to the GPU, including 2D rendering, where many operations are considerably faster.