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Faking a JPEG

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341 points todsacerdoti | 1 comments | 11 Jul 25 22:57 UTC | HN request time: 0.234s | source
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puttycat ◴[12 Jul 25 02:01 UTC] No.44538667[source]▶
> compression tends to increase the entropy of a bit stream.

Does it? Encryption increases entropy, but not sure about compression.

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JCBird1012 ◴[12 Jul 25 02:13 UTC] No.44538728[source]▶
I can see what was meant with that statement. I do think compression increases Shannon entropy by virtue of it removing repeating patterns of data - Shannon entropy per byte of compressed data increases since it’s now more “random” - all the non-random patterns have been compressed out.

Total information entropy - no. The amount of information conveyed remains the same.

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1. gary_0 ◴[12 Jul 25 08:10 UTC] No.44540229[source]▶
Technically with lossy compression, the amount of information conveyed will likely change. It could even increase the amount of information of the decompressed image, for instance if you compress a cartoon with simple lines and colors, a lossy algorithm might introduce artifacts that appear as noise.