this post was submitted on 29 Mar 2025
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[–] AbouBenAdhem@lemmy.world 49 points 2 months ago (13 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?

[–] zerofk@lemm.ee 5 points 2 months 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.

[–] AbouBenAdhem@lemmy.world 1 points 2 months 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.

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