Issue: Version 3.6 (pre-release) does not seem to support .webp images

[Thundercraft]

Looking at the Version History page:
https://www.sumatrapdfreader.org/docs/Version-history
Under "next (3.6) #" I find:

Changes in pre-release builds:

register for handling .webp files

Perhaps that register is just an early step towards .webp support and, by itself, is not enough to display WebP images? After installing the latest 3.6 build, I used it to read an .epub I created with .webp images. (I made sure that the "document.opf" in my .epub had the media-type="image/webp" for those images, telling it to decode the images as webp.)
Sadly, it would not display those images at all. It just showed them as [IMAGE].

As a test, I tried reading my .epub with .webp images through some online EPUB readers. One of those failed, but at least 3 others displayed the images. (Though, in one the images were too small and in another the images were too big, being cropped off the edges.) But this test did verify that .epub should support .webp and my .epub file does work in viewers designed to handle .webp.

I see this as unfortunate as the WebP format allows for a much better image compression to quality ratio compared to other formats like JPEG. There is even an option to store images in a lossless format. WebP is clearly an image format with a bright future.

What's frustrating is that the EPUB standard has had at least partial support for WebP for years. On December 4, 2020, the EPUB 3 Working Group provisionally declared WebP as a "draft" format, marking the beginning of its official consideration for the standard. And in May 2023, with EPUB 3.3, WebP was officially included as a supported media format. But even before 2023, some EPUB software and apps had limited support of WebP through the use of fallback images: The EPUB standard allows you to include a fallback image in a widely supported format, such as JPEG, for devices that cannot render WebP.

Anyway, my experience of trying to get EPUB readers to properly display .webp has severely soured my enthusiasm for WebP and on what I was working on. So, for now, I guess I'll stick with JPEG. I could find an alternative EPUB reader to display my file. But since WebP support is still not widely available, using WebP images in my documents would severely limit who can view them properly.

[GitHubRulesOK]

seem to remember there was a long protracted issue about them but they have a checkered reputation #3415 and not considered a good format for other than online use so once proven "fit for other purpose" more likely to be wider supported but not PDF which is headed towards googles other newer compression (brotli)

however, the point about compression is one person saves a second packing a file and 8 billion users waste seconds decompressing them to read or view the content as uncompressed images or text

I asked AI to calculate the minimal loss expected from using compression and decompression globally and of course its on the low side of caution as only about 50% of compressed pages are presumed to be ever read.

How hot is the carbon? Lukewarm. About 0.22 tonnes CO₂e/year in this conservative setup—roughly a fifth of a standard 1‑tonne carbon credit.
How many graves? About one “grave” per year in lives-equivalent—driven not by electricity, but by the aggregate seconds lost to decode/encode.

means nothing to me but the calculation was Cost and lives-equivalent 𝐶𝑡𝑖𝑚𝑒=𝑣⋅𝐻,𝐶𝑒𝑛𝑒𝑟𝑔𝑦=𝑐𝑘𝑊ℎ⋅𝐸𝑦𝑒𝑎𝑟,𝐿=𝐶𝑡𝑖𝑚𝑒+𝐶𝑒𝑛𝑒𝑟𝑔𝑦𝑉𝑆𝐿

but if we assume 50 lives wasted over 50 years that's 50 too many lifetimes wasted and much of that has been mine.