Image Compression

Don't sleep on JPEG XL. It's used under the hood within DNG files (at least, it's an option, Adobe DNG Converter can leverage it, including by the CLI), DxO PureRAW leverages it in the latest versions. Apple Photos can view them, and I think it's been the compression methodology used inside their ProRAW DNGs for a while (which probably by default makes it one of the worlds most popular image compressors for RAW files). I've had a lot of success using it for various things. Had some issues surrounding metadata but that may be user error on my part.

Worth highlighting the QOI Image format (qoiformat.org) showing that you can also get significant image compression benefits with a simple 1-page specification [1]:

> QOI is fast. It losslessly compresses images to a similar size of PNG, while offering 20x-50x faster encoding and 3x-4x faster decoding.

> QOI is simple. The reference en-/decoder fits in about 300 lines of C. The file format specification is a single page PDF.

[1] https://qoiformat.org/qoi-specification.pdf

> Now that WebP is widely supported by browsers and operating systems, there's really no downside to using it. It's much more flexible than JPEG or PNG and offers better compression than both of them.

I'd probably skip WebP, and go straight to AVIF at this point. I believe all modern browsers support it, and it compresses better than WebP.

I love image and video compression. For fun, I made my own and managed to squeeze an image of myself into byte level file sizes.

It's amazing to me how we much we can fill in the blanks to make something recognizable with such little data.

I recently built a small image optimizer for macOS since ImageOptim is mostly abandonware now. Specifically for folks who dislike complex build tools for this job https://shiboru.com

Most comprehensive write up of JPEG et al. I have ever come across.

I think the MozJPEG compression optimisations deserves a mention, as does where we started, with RLE encoding for printer things.

Also important for my personal understanding of JPEG is the context: slow CPUs and analogue screens. OG JPEG was optimised for this, MozJPEG changed the look up tables and the ubiquitous 'turbo' JPEG library to use a few more CPU cycles and save a few more bytes, whilst fixing the banding that was actually okay in the analogue days of old CRT monitors.

Bookmarked the article for re-reading.