Provide screenshot format: AVIF and arbitrarily large tiled image (using grid derivation)

[JW1]

Since we can now view images in AVIF format with Firefox, and together with other mainstream web browsers AVIF become a portable image format, it would be great to make a screenshot directly in this format.

What's more, AVIF (and the proprietary HEIC) supports big tiled images like TIFF but this format is more flexible and allows both good compression ratio and fast decoding. I'd love to make a (lossless) full page screenshot and save it as one single image file of a much smaller file size than it is using PNG images.

I'm also an extension developer (of Screenshot2HTML) and I hope this new format is also added to the API `browser.tabs.captureTab()`. 😁

[Jon]

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[sfoster]

Thanks for this suggestion. Proving a way to support arbitrarily large screenshots using tiling does seem interesting. The constraints we work under today mean that full page captures - especially on high density displays or > 100% zoom level - are sometimes impossible. 

Whether AVIF would yield an improvement with regards to compression and encoding/decoding I assume would depend on the page being captured. One of the reasons we removed the .jpeg output in favor of always returning .png was because *most* pages, most of the time are not photographic in nature, where JPEG (and AVIF as I understand it) really shine.

I'm not opposed in principle to providing the user the ability to choose the format they want, but we have to balance that additional step and complexity with providing a simple, decision-free workflow for frequent operations.

We're also considering adding support for short screencast kind of animated or video captured from the screen over time. AVIF might be a good candidate to consider there.