mozjpeg VS libjpeg-turbo

[2] https://github.com/mozilla/mozjpeg

It would be nice if the author would add mozjpeg[1] to the comparison. At certain sizes, it can produce smaller sizes than WebP, and because it is still a jpeg, it has a much better compatibility story, which the author alluded to.

[1]https://github.com/mozilla/mozjpeg

image-shrinker is a simple, easy to use open source tool for shrinking images. Under the hood it uses pngquant, mozjpg, SVGO, and gifsicle. You can also install these tools individually if you need to compress some images. I often use pngquantafter exporting PNGs for web projects from Figma or similar tools. I literally run it like this:

> MozJPEG is a patch for libjpeg-turbo. Please send pull requests to libjpeg-turbo if the changes aren't specific to newly-added MozJPEG-only compression code.

https://github.com/mozilla/mozjpeg#mozilla-jpeg-encoder-proj...

FWIW, Mozilla has been maintaining their own fork for quite a while now[1]

AFAIK most Linux Distros have been using libjpeg-turbo as a drop-in replacement for libjpeg, after some drama in ~2010 where libjpeg came under new management, decided to break ABI/API several times over and add incompatible, non-standard format extensions[2].

[1] https://github.com/mozilla/mozjpeg

[2] https://en.wikipedia.org/wiki/Libjpeg#History

No.

See https://github.com/mozilla/mozjpeg

Also, there is a fairly big problem with JPG that the ‘quality’ setting is not calibrated. That is you might look at one image and think it looks fine (which is subjective, depends on what you want to use the image for…) with a quality of 60%, but then you compress a million images at that rate, delete the originals, then you find that many of them look really awful. Not only that but there are images you could have compressed more and still been happy with the output.

If you are publishing images for the web consider using WebP which is consistently better, well supported now, and has a calibrated quality knob.

https://github.com/mozilla/mozjpeg's cjpeg tool is the command line version of the mozjpeg library, itself a fork of libjpeg-turbo. Mozjpeg performs lossless JPEG optimization. There are plenty of others out there.

Use the Mozilla JPEG Encoder, which implements several tricks for smaller file size / better visual quality. The result is still JPEG standard compatible that other software can decode.

Guetzli was already mentioned and roughly does what you are talking about.

MozJPEG [1] includes several quantization tables that are optimized for different contexts (see the quant-table flag and source code for specific tables[2]), and the default quantization table has been optimized to outperform the recommended quantization tables in the original JPEG spec (Annex K).

It's also worth noting that MozJPEG uses Trellis quantization [3] to help improve quality without a per-image brute force quantization table search. Basically rather than determining an optimal quantization table for the image, it minimizes rate distortion on a per-block level by tuning the quantized coefficients.

[1] https://github.com/mozilla/mozjpeg

[2] https://github.com/mozilla/mozjpeg/blob/5c6a0f0971edf1ed3cf3...

[3] https://en.wikipedia.org/wiki/Trellis_quantization

They're still being used. A newer, optimized JPEG encoder, mozJPEG[0], seems to use progressive encoding by default. I suspect with faster internet speeds, most images download and decode so fast that the cool 'enhance' animation doesn't happen anymore.

[0] https://github.com/mozilla/mozjpeg

> all decoders will render the same pixels

Not true. Even just within libjpeg, there are three different IDCT implementations (jidctflt.c, jidctfst.c, jidctint.c) and they produce different pixels (it's a classic speed vs quality trade-off). It's spec-compliant to choose any of those.

A few years ago, in libjpeg-turbo, they changed the smoothing kernel used for decoding (incomplete) progressive JPEGs, from a 3x3 window to 5x5. This meant the decoder produced different pixels, but again, that's still valid:

https://github.com/libjpeg-turbo/libjpeg-turbo/commit/6d91e9...

Last vestiges of this fact AFAIK were libjpeg, which had a macro NEED_SHORT_EXTERNAL_NAMES that shortens all public identifiers to have unique 6-letter-long prefixes. Libjpeg-turbo nowadays has removed them though [1].

[1] https://github.com/libjpeg-turbo/libjpeg-turbo/commit/52ded8...

While I think the move to safer code through Rust and other alternatives is a nice breath of fresh air, I doubt you can get these kinds of optimization without using unsafe code in Rust. These optimized implementations often require some kind of safety-bypassing memory modifications to work as efficiently ad they do.

There's a reason https://github.com/libjpeg-turbo/libjpeg-turbo/tree/main/sim... is filled with assembly files with conditional loading.

Sure. You'll see it very often in codec implementations. From rav1e, a fast AV1 encoder mostly written in Rust: https://github.com/xiph/rav1e/tree/master/src/x86

Large portions of the algorithm have been translated into assembly for ARM and x86. Shaving even a couple percent off something like motion compensation search will add up to meaningful gains.

Or the current reference implementation of JPEG: https://github.com/libjpeg-turbo/libjpeg-turbo/tree/main/sim...

zune-jpeg is 1.5x to 2x faster than jpeg-decoder and is on par with libjpeg-turbo.

This is interesting from the standpoint of how new JVM features can be used to improve performance (what I presume the article's main purpose to have been), but the image processing improvement itself isn't head-turning. Also, we've found that libjpeg-turbo (https://libjpeg-turbo.org/) is ~5x (IIRC, can re-run my JMH benchmark if anyone wants me to) as fast for decoding JPEGs as ImageIO, so we wouldn't even benefit from this change in 21 much.

libjpeg-turbo: https://github.com/libjpeg-turbo/libjpeg-turbo/blob/main/simd/x86_64/jsimdcpu.asm

libjpeg-turbo

For all but the simplest formats (basically BMP), the difficulty of implementing encoding/decoding from scratch is significant - well beyond a beginner's ability, and challenging/time-consuming even for senior developers. So, libraries are used in practice - e.g. libpng and libjpeg-turbo.