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A comment on The Near-Lossless Image Formats Using Ultra-Fast LZ Codecs.

Re:The Near-Lossless Image Formats Using Ultra-Fast LZ Codecs by taylorius on Monday April 03, 2023 @06:56AM (#35421432)
In the article Richard shows us the compression stats for the png algorithm vs lz4, for the original lossless image. It would also be interesting to see how the png algorithm performs on the lossy, preconditioned versions of the image. Does it also get any benefit, or does lz4 pull ahead?
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Re:The Near-Lossless Image Formats Using Ultra-Fast LZ Codecs by silvestrov on Monday April 03, 2023 @07:28AM (#35421715)
Very little, you can check by downloading the images as the LZ4 images has been reencoded into PNG so the browsers can show them.

Orig PNG: 1443667 bytes. Lossy LZ4I = 1433231, delta = -10436 bytes. A more lossy LZ4I = 1344183, delta = -99484 bytes from PNG.

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Re:The Near-Lossless Image Formats Using Ultra-Fast LZ Codecs by taylorius on Monday April 03, 2023 @08:06AM (#35422088)
Ah, good call, thank you. Of course he would use png for browsers!
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Re:The Near-Lossless Image Formats Using Ultra-Fast LZ Codecs by 1ko on Monday April 03, 2023 @08:08AM (#35422117)
That is because the png are not optimized, using lossless PNG compression (OxiPNG + AdvPNG) I get the Lossy LZ4I down to 696819 bytes.
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Re:The Near-Lossless Image Formats Using Ultra-Fast LZ Codecs by bscphil on Monday April 03, 2023 @01:16PM (#35427616)
Yes, thank you for pointing this out. To be more precise about it:

    Original PNG:    1310987 bytes
    Lossy PNG:       1154386 bytes (90.4% of LZ4i)
    Lossy LZ4i:      1276477 bytes
    More Lossy PNG:   693278 bytes
    More Lossy LZ4i:  818774 bytes (84.7% of LZ4i)
So it's notable that this lossy PNG technique has diminishing returns for LZ4i - it actually becomes more effective as a PNG preprocessor as you get more lossy, relative to LZ4i!

Still, there's a decent argument that PNG is no longer Pareto-optimal. There's stuff that gets close to the same compression ratio but decompresses much faster, and there's stuff that compresses much better and is also lossless, e.g. JPEG-XL lossless mode.

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