4 ms·

I keep a list of the most efficient lossless PNG optimizers, and Zopfli is definitely one of the best. https://olegkikin.com/png_optimizers/ https://olegkikin.

• masklinn 11y ago
  Unsurprisingly, PNGOut, ZopfliPNG and AdvanceCOMP all use non-zlib DEFLATE implementations (respectively pkzip, zopfli, and 7zip or zopfli depending on setting). Interestingly, as far as I know OptiPNG uses the standard zlib DEFLATE and still closes in on the lead optimisers for all but picture 3. Although it would be good to include more information about your compression parameters: while OptiPNG -o7 doesn't do anything to picture 3, a complete exhaustive search (-o7 -zm1-9) does manage to compress it down to 8724 bytes (8471 IDAT) edit: in fact, despite the help text's claim, optipng shows a very slight improvement on the first three pictures by using the strongest most exhaustive search parameters (compared to those you list, using optipng 0.7.6): * Picture 1 9787 bytes (51.80%) versus 9979 (50.85%) * Picture 2 20513 bytes (10.63%) versus 20671 (9.94%) * Picture 3 8724 bytes (10.09%) versus 9703 (0%) Pictures 4 and 5 compress to the sizes you listed even using exhaustive searching.