Free Universal Image Format (FUIF)

[SolidComp]

Jyrki tweeted about this, and I thought y'all would be interested: https://github.com/cloudinary/fuif

From their Readme:

FUIF supports several methods for image preprocessing and entropy coding, so it can use the methods that work best for a particular image (or a particular part of an image).

For non-photographic images with few colors, a palette (color index) can be used. There is no limit on the palette size.

For images with repetition (e.g. images that include text, where the same letter shapes appear in multiple locations), an optional transformation can be used to replace repetition with references (somewhat similar to JBIG2).

For photographic images, the DCT transformation can be used.

[Piotr Tarsa]

There's some interesting statement:

'Honest' compression artifacts. There are various approaches to how to do lossy compression. Different techniques lead to different artifacts. Some artifacts are less "annoying" than other artifacts. For example, blurring, smearing and mild ringing are probably not very annoying (or even desireable to some, because it might eliminate noise and increase perceived sharpness), while pixelation, blockiness and color banding are annoying and obvious compression artifacts. Also, some artifacts are not very "honest", in the sense that the image looks deceptively better than it actually is. For example, JBIG2 in lossy mode or HEIC at low bitrates can produce images that look like they are high-quality (e.g. they have sharp details at the pixel level), but they are actually very different from the uncompressed image. For example, JPEG artifacts are "honest" and "annoying", while WebP and HEIC artifacts are "not honest" and "not annoying". FUIF aims for compression artifacts that are "honest" and "not annoying". At low bitrates, pixelation will become obvious at a 1:1 scale, but the overall image fidelity will still be as high as possible (e.g. comparing a downscaled lossy FUIF image to a downscaled original). Rationale: this is a matter of preference, but we think that image fidelity is more important than hiding the fact that lossy compression was used. An image format should not act as an artistic filter that modifies an image more than necessary. At least that's our opinion.

Do you have examples of "not honest" artifacts in HEIC images? I managed to find JBIG2 images that expose a flaw that can be considered "not honest" (scanned documents have some digits replaced with another ones).

[Jyrki Alakuijala]

(scanned documents have some digits replaced with another ones).

Yes, that is a classic example of small error in PSNR but a big error in the bottom line.

I have seen an x265 implementation to copy image areas from elsewhere in the image which might cause similar issues but at lower contrast information.