PNG-spec
libjxl
PNG-spec | libjxl | |
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4 | 85 | |
42 | 2,236 | |
- | 28.2% | |
8.9 | 9.8 | |
13 days ago | about 12 hours ago | |
HTML | C++ | |
GNU General Public License v3.0 or later | BSD 3-clause "New" or "Revised" License |
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PNG-spec
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Hello, PNG!
Pull requests welcome. :D
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Are IDAT chunks in PNG encoded individually?
There are multiple github issues on the subject where we work on future editions of the PNG spec. (3rd Edition coming soon!)
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Google Chrome Is Already Preparing To Deprecate JPEG-XL (~3x smaller than JPEG, HDR, lossless, alpha, progressive, recompression, animations)
Especially enticing as the PNG file format does allow for additional compression/filter methods and new ones could be added to a PNG 2.0 standard. A small wishlist discussion about that at the W3C's PNG specification Github.
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QOI – The “Quite OK Image Format” for fast, lossless image compression
> But its not like any reader ever supports it fully, hell most readers dont support showing the other images in a png file.
Do you mean APNG? In all fairness, that is not even in the specification although there is discussion to add it. https://github.com/w3c/PNG-spec/issues/26
The one that was specified was MNG but it was a different format and practically no one used it since it was not parsable as a PNG.
libjxl
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JPEG XL and Google's War Against It
> Regarding JPEG XL's mobile support, it makes sense it would see limited development if the company that manages one of the biggest mobile players has been the greatest restriction on their success. The lack of support also disincentivises manufacturers to prioritise support.
There was literally no involvement from any hardware vendor in the standardization of JPEG XL. It went from a Call for Proposals in Sept 2018 to Committee Draft in Aug 2019 with very little time for industry feedback. Contrast this with AV1 which had involvement from hardware vendors Intel, NVIDIA, Arm, AMD, Broadcom, Amlogic from the beginning as well as companies who ship media on hardware at scale such as Cisco, Netflix, Samsung and yes Google. These companies reviewed and provided significant feedback on the format that made it suitable for hardware implementation.
https://news.ycombinator.com/threads?id=JyrkiAlakuijala is a lead on the project and a Google employee, and active in JPEG XL development https://github.com/libjxl/libjxl/commits?author=jyrkialakuij...
- JPEG XL Reference Implementation
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JPEG XL and the Pareto Front
https://github.com/libjxl/libjxl/blob/main/doc/format_overvi... is a pretty detailed but good overview. The highlights are variable size DCT (up to 128x128), ANS entropy prediction, and chroma from luminance prediction. https://github.com/libjxl/libjxl/blob/main/doc/encode_effort... also gives a good breakdown of features by effort level.
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Compressing Text into Images
For JPEG XL, refer to its format overview [1]. In short its lossless mode uses a combination of multiple techniques: the rANS coding with an alias table, LZ77, reversible color transforms, a general vector quantization that subsumes palettes, a modified Haar transform and a learnable meta-adaptive decision tree for context modelling.
One good thing about JPEG XL is that its lossy mode also largely uses the same tool, with a major addition of specialized quantization and context modelling for low- and high-frequenty components.
[1] https://github.com/libjxl/libjxl/blob/main/doc/format_overvi...
- JPEG XL v0.9.0 Released
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Stripping Metadata
The cjxl source is here. If you spot any reason why -x strip=exif may not work, tell me.
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Www Which WASM Works
The problem is that the instructions for actually running the WASM file are not that clear... the docs the author mentions shows how to compile to WASM, which is easy enough, but then here's the instructions to make that actually work in the browser:
https://github.com/libjxl/libjxl/blob/main/tools/wasm_demo/R...
Yeah, you need some mysterious Python script, a JS service worker at runtime, choose whether you want the WASM or WASM_SIMD target, use a browser that supports Threads and SIMD if you chose that, make sure to serve everything with the appropriate custom HTTP headers... just reading that, I can see that to get this stuff working on non-browser WASM targets would likely require expertise in WASM, which is the point of the OP. WASM's UX is just not there yet.
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First automatic JPEG-XL cloud service
https://github.com/libjxl/libjxl#usage
> Specifically for JPEG files, the default cjxl behavior is to apply lossless recompression and the default djxl behavior is to reconstruct the original JPEG file (when the extension of the output file is .jpg).
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Why "sudo make install"?
I mean compiling a bleeding edge kicad, inkscape or jpeg-xl is easy. But will probably trash your system if you already have an older version installed.
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XYB JPEG: Perceptual Color Encoding Tested
But you look at your image viewer that could have the lossless indicator? (and there is an issue open to add this indicator to the jxl files)
https://github.com/libjxl/libjxl/issues/432
What are some alternatives?
qoi - The “Quite OK Image Format” for fast, lossless image compression
fpng - Super fast C++ .PNG writer/reader
Android-Image-Filter - some android image filters
zopfli - Zopfli Compression Algorithm is a compression library programmed in C to perform very good, but slow, deflate or zlib compression.
DirectXMath - DirectXMath is an all inline SIMD C++ linear algebra library for use in games and graphics apps
spdx-spec - The SPDX specification in MarkDown and HTML formats.
libavif - libavif - Library for encoding and decoding .avif files
specification - Solid Technical Reports
jxl-migrate - A simple Python script to migrate images to the JPEG XL (JXL) format
jpeg2png - silky smooth JPEG decoding
squoosh - Make images smaller using best-in-class codecs, right in the browser.