Tag: Image

Edit (2023-03-30): Added a couple extra images to test for high-quality encoding and illustrations. Introduce SSIM and MSE measures.

Edit (2023-03-03): Fixed mistake, as AVIF does in fact NOT support progressive decoding.

Edit (2024-01-24): Following a comment on Mastodon, I have added a reference on the good performance of lossless WebP.

JPEG XL and AVIF are arguably the two main contenders in the battle to replace JPEG as the next-generation image format. There are other formats in the race, like HEIC and WebP 2, but the former is subject to licensing patents (and possibly not royalty-free), and the second is still in development and seems that it may never see the light of day as a production-ready image format anyway. The original WebP is not even a contender as it is inferior to AVIF in almost all aspects¹ (although it may be ok in lossless compression²), and you should probably never use it for photography anyway³, or at all if you are not ok with mediocre image quality.⁴

First, a quick browser support test:

If you are browsing this page around 2023, chances are that your browser supports AVIF but does not support JPEG XL. This is mainly due to the Chrome team dropping support for JPEGL XL against the opinion the community at large. In this post, I hope to convince you why this is a bad move. Below, I perform a quick analysis of lossless and lossy compression with JPEG XL and AVIF, and evaluate how they fare in terms of file size and visual quality.

Edit (2023-04-05): Added some suggestions by the author/developer of libvips.

Today I discovered libvips, a command line utility and library to manipulate and process images, and I am impressed. I’ve been using ImageMagick and its fork, GraphicsMagick, for as long as I have had to process images from the CLI, and they work well for moderately-sized images. But lately, I have been preparing virtual texture datasets for Gaia Sky and the sizes of my images have increased exponentially. Right now I’m processing 64K and 128K images on the regular (that is 131072x65536 pixels), and ImageMagick just can’t do it reliably. It uses so much memory that it can’t even split a 64K image in a 32 GB RAM machine without running out of it. Running it with the suggested options to limit memory usage (--limit memory xx mb, etc.) and use a disk cache never works for me. It just produces blank images for some reason. So after implementing a couple of Python scripts based on OpenCV and NumPy to do some basic cropping, I took on the task of finding a proper, capable replacement. And found it I did. Libvips is the perfect tool, it seems. Based on my few first tests, it performs much better than ImageMagick and GraphicsMagick. It is super fast and never seems to use much memory, no matter how big an image I throw at it.

The web is currently based around the JPEG, PNG and GIF image formats. These are all very old and suboptimal formats which were never designed in the first place with the modern web in mind. A few newer competing formats have popped up recently, aiming to dethrone the original trio to postulate themselves as the standard web image format of the future. These are, essentially, WebP (.webp extension), developed by Google and hated by almost everyone else, AVIF (.avif extension), based on the AV1 container and developed by the ‘Alliance for Open Media’, a conglomerate of big tech companies that are anything but open, and JPEG XL (.jxl extension), developed by the Joint Photographic Experts Group, the same people that developed the original JPEG.

So what’s the fuss all about? Recently, Google decided to kill JPEG XL support in Chrome. A full report follows.