After reading your article I got zopfli-cryopng here:
After many hours of tweaking, I was able to produce the ultimate optimized small size PNG files...and then I tried WebP - in seconds I had a lossless WebP file smaller than the best PNG I could produce from any of the best PNG optimization tools. So, I think I'll be using WebP for all of my lossless needs from now on.
For lossy images, JPEG does a pretty good job. To beat JPEG, I've been testing BPG and WebP. So far, it appears BPG is capable of producing smaller sizes, but it takes a lot of tweaking to get it optimized to match or beat the quality of JPEG at an equal or smaller size. BPG reminds me of all the tweaking I had to do for PNG, but BPG does indeed produce better quality at smaller sizes compared to JPEG. Compared to WebP, BPG still has a slight edge, but once again, WebP is much easier to use. Hours of tweaking and detailed image comparisons with BPG are unnecessary with WebP. Still, BPG was able to beat WebP in my tests, but I think I liked the simplicity of WebP much more.
The area where BPG has no rival is in animated images. Making a BPG animation is almost as easy as making an animated GIF, but the small amount of extra effort in making a BPG gives AMAZING reductions in file sizes and UNBELIEVABLY HUGE increases in quality, compared to GIF. Of course, that should be no surprise, since GIF is an obsolete dinosaur, and has been for decades. What I'm trying to do now is compare BPG animations with MP4 and WebM video. Producing frame-by-frame optimized video is a bit harder in MP4 and WebM (with or without audio) compared to GIF and BPG (no audio), but my preliminary results thoroughly trounce GIF also. If I stopped here, I could replace low-resolution low-framerate silent animated GIF's with high resolution high framerate MP4 and WebM at the same file size.
WebM probably beats MP4, but I will need to do more testing to see if WebM beats BPG. I'm guessing the browser support for WebM could make it my first choice, and of course it will pair nicely with WebP. With WebM and lossless WebP already appearing to serve most needs, I'm basically figuring out if BPG beats those, and/or if any of them beat JPEG. At high lossy quality levels, JPEG is still pretty competitive with lossy WebP and BPG. WebP's edge over JPEG is small, and so far it hasn't motivated the world to abandon JPEG in favor of WebP. BPG's edge over JPEG is larger, but once again, it might not be enough at high quality levels to motivate abandoning JPEG. With low lossy quality levels, both WebP and BPG beat JPEG, but if we want better quality, we can still get it with JPEG without needing any new formats.
At the end, the only thing I'm confident of is that WebP beats PNG, and it does it with a lot less effort. I only did a few photographic tests, so maybe there are circumstances where PNG beats WebP, but then I think the convenience of WebP would probably make me say "meh, I don't care, I'm using WebP anyway, because it's easier".
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