changelog
1.25 — 08/09/2025 | see notes
optimization of implementations
1.24.x — 08/08/25
2 - 08/08: small improvements for c3, fix compression regressions (vs 1.2.3.9)
1 - 25/07: improved PNG filtering (+0.31% compression / +1.58% speed on corpus)
1.24 — 22/07/2025
fixed heuristic for transforms
fixed palette sorting issue
improved text/noise transform
1.23.x — 26/06/2024
improved PNG and WebP lossless further (palette)
improved alpha-p palette optimization
added already optimized palette from PNG
heuristic for PNG > WebP lossless
changed already optimized palette from PNG
(1.23.9)
fixed -s1 for mt-palette
fixed JPEG q heuristic for transforms
fixed near gray
1.23 — 21/04/2024
improved PNG lossless further (palette)
improved WebP lossless (palette)
1.22 — 18/04/2024
fixed & improved PNG lossless (palette)
1.21 — 15/04/2024
added lossy & keep alpha
fixed WebP lossy does not keep alpha with -noalpha
changed % considering processable files only
various code optimization
1.20 — 20/03/2024
improved grayscale+alpha lossless filtering
changed behavior of -hq=1 on flat
improved lossy on near-grayscale images
fixed critical-typo when grayalpha in fast lossless
fixed & improved fast lossless
fixed compression regression from c6
fixed crash
1.19 — 07/03/2024
small improvements for palette sorting (PNG/WebP)
fixed & improved near-lossless (-hq) (PNG/WebP)
1.18 — 27/02/2024
improved heuristic in auto (PNG/JPEG)
improved -grayline/scale
fixed -hq behavior
various code optimization
1.17 — 13/01/2024
changed grayscale formula + fixes
1.16 — 15/11/2023
fixed and improved auto with palette as input (PNG/WebP)
1.15 — 30/10/2023
fixed palette stuff 3 (PNG)
1.14 — 26/10/2023
fixed palette stuff 2 (PNG)
1.13 — 25/10/2023
fixed palette stuff (PNG)
1.12 — 22/09/2023
reintroduced near stuff -hq=N (PNG/JPEG/WebP)
improved lossless content-heuristic (PNG)
1.11 — 23/08/2023
improved -s0 lossless for paletted (PNG)
1.10 — 22/08/2023
fixed handling of invalid APNG structure
improved conversion when using -grayscale and auto (APNG/PNG)
improved auto decisions (APNG/PNG/WebP)
1.09 — 01/08/2023
fixed incorrect APNG optimization (size)
1.08 — 25/07/2023
fixed filter in auto (WebP)
1.07 — 25/07/2023
fixed grayscale and lossy (JPEG/WebP)
1.06 — 08/07/2023
improved heuristics for truecolor even more (WebP)
1.05 — 07/07/2023
fixed rotation and lossy (JPEG/WebP)
fixed some heuristics & improvements for truecolor stuff (WebP)
improved default efficiency for lossless WebP (-s0)
1.04 — 06/07/2023
improved auto decisions (PNG/WebP)
1.03 — 23/06/2023
improved auto decisions (PNG/WebP)
1.02 — 19/06/2023
fixed metadata (copy)
1.01 — 19/06/2023
fixed metadata handler -nostrip
1.00 — 14/06/2023 | see notes
initial 1.x release