ORG.IPEP:
Rate-Distortion Optimized Lossy PNG and QOI Encoding Tool (rdopng)
rdopng is a command line tool which uses LZ match optimization, Lagrangian multiplier rate distortion optimization (RDO), a simple perceptual error tolerance model, and Oklab-based colorspace error metrics to encode 24/32bpp PNG files which are 30-80% smaller relative to lodepng/libpng. The tool defaults to reasonably fast near-lossless settings which writes PNG's around 30-40% smaller than lossless PNG encoders.
Unlike pngquant, rdopng does not use 256-color palettes or dithering. PNG files encoded by rdopng typically range between roughly 2.5-7bpp, depending on the options used (and how much time and patience you have).
Some example encodes and command lines are here.
You can download a pre-built Windows binary here. You may need to install the VS 2022 runtime redistributable from Microsoft.
| aliens.png [499788] |
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| aliens_rdo.png [261332] |
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| aliens_2_rdo.png [206448] |
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| crossyf.png [897010] |
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| crossyf_rdo.png [323624] |
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| crossyf_2_rdo.png [265207] |
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| doom.png [464665] |
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| doom_rdo.png [279841] |
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| doom_delta.png [320663] |
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| gotham.png [591247] |
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| gotham_rdo.png [192478] |
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| gotham_delta.png [554380] |
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| gotham_2_rdo.png [171885] |
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| gotham_2_delta.png [595632] |
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| high_fidelity.png [514995] |
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| high_fidelity_1.png [363467] |
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| high_fidelity_2.png [188568] |
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| joker_768.png [339338] |
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| joker_768_rdo.png [137253] |
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| joker_768_delta.png [362749] |
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| joker_768_2_rdo.png [165524] |
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| joker_768_2_delta.png [339650] |
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| joker_768_3_rdo.png [225803] |
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| joker_768_3_delta.png [280948] |
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| joker_768_4_rdo.png [99386] |
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| joker_768_4_delta.png [374280] |
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| kodim18.png [777096] |
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| kodim18_rdo.png [235597] |
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| kodim18_delta.png [624582] |
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| lara_1024.png [1500821] |
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| lara_1024_rdo.png [1201499] |
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| lara_1024_delta.png [666483] |
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| magneto.png [153318] |
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| magneto_rdo.png [84790] |
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| magneto_delta.png [117630] |
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| magneto_2_rdo.png [72941] |
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| magneto_2_delta.png [105569] |
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| magneto_2_alpha_delta.png [4000] |
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| masterchief.png [448582] |
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| masterchief_rdo.png [214551] |
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| masterchief_2_rdo.png [172080] |
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| minerology.png [888458] |
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| minerology_rdo.png [622869] |
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| minerology_delta.png [487981] |
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| puppy.png [1567850] |
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| puppy_rdo.png [593962] |
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| puppy_delta.png [1278004] |
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| stp.png [785006] |
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| stp_rdo.png [412128] |
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| stp_delta.png [709160] |
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| stp_2_rdo.png [321873] |
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| stp_2_delta.png [778349] |
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| stp_3_rdo.png [289303] |
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| stp_3_delta.png [788024] |
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| waterfall.png [2074607] |
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| waterfall_rdo.png [1202930] |
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| waterfall_delta.png [1430319] |
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| xfiles_768.png [500148] |
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| xfiles_768_rdo.png [301910] |
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| xfiles_768_delta.png [355589] |
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| xfiles_768_2_rdo.png [169558] |
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| xfiles_768_2_delta.png [458052] |
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