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199

Beyond RGB: A new image file format efficiently stores invisible light data (arstechnica.com)

submitted 5 days ago by [email protected] to c/[email protected]

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[–] [email protected] 40 points 5 days ago (3 children)

Spectral JPEG XL utilizes a technique used with human-visible images, a math trick called a discrete cosine transform (DCT), to make these massive files smaller [...] it then applies a weighting step, dividing higher-frequency spectral coefficients by the overall brightness (the DC component), allowing less important data to be compressed more aggressively.

This all sounds like standard jpeg compression. Is it just jpeg with extra channels?

[–] [email protected] 31 points 5 days ago (1 children)

Yeah, it compresses better too though, and jpeg XL can be configured to compress lossless, which I imagine would also work here

[–] [email protected] 5 points 5 days ago (2 children)

Lossless JPEG would be amazing.

[–] [email protected] 5 points 4 days ago

JPEG 2000 supports lossless mode.

[–] [email protected] 3 points 4 days ago (1 children)

In my experience, as you increase the quality level of a jpeg, the compression level drops significantly, much more than with some other formats, notably PNG. I'd be curious to see comparisons with png and gif. I wouldn't be surprised if the new jpeg compresses better at some resolutions, but not all, or with only some kind of images.

[–] [email protected] 3 points 4 days ago

jpeg xl has been in development from FLIF for like 15 years there are tons of comparisons all over, even live ones on youtube

[–] [email protected] 5 points 4 days ago (1 children)

Kind of, but JPEG converts image data to its own internal 3 came channel colour space before applying DCT. It is not compressing the R, G and B channels of most images. So a multichannel compression is not just compressing each channel separately.

[–] [email protected] 1 points 4 days ago

Yeah, jpeg converts to lab (or something similar, I think). But the dimensions are the same: one channel for lightness, and then a number of channels one less than the total number of sampled frequencies to capture the rest of the color space.

[–] [email protected] 3 points 4 days ago* (last edited 4 days ago)

It's not just like jpeg with extra channels. It's technically far superior, supports loss less compression, and the way the decompression works would make thumbnails obsolete. It can even recompress already existing JPEGs even smaller without additional generation loss. It's hard to describe what a major step this format would be without getting very technical. A lot of operating systems and software already support it, but the Google chrome team is practically preventing widespread adoption because of company politics.

https://issues.chromium.org/issues/40168998