png_minifier 1.0.0

Minify PNG images in pure Dart: many optimisation strategies compete and the smallest result that meets the quality target wins. Lossless by default, bounded-error palette quantisation on request; det [...]

1.0.0

• First release: minify PNG images in pure Dart.
  • Many strategies compete per image; the smallest result meeting the quality target wins, with the input returned when nothing is smaller.
  • Lossless strategies: transparent-pixel cleanup, colour-type and bit-depth reduction (RGB, greyscale 1–16 bits, grey+alpha, tRNS colour keys), indexed palettes at 1/2/4/8 bits, three palette orders, seven PNG filter strategies, deflate-level search.
  • Lossy strategies, each checked against the quality before it may win: frequency palette (pixel art), median cut, k-means, bounded Floyd–Steinberg dithering, posterize, alpha snapping.
  • Quality: PngQuality.lossless() (default), .maxError(n), .psnr(dB), .bounded(...) or a TinyPNG-like .level(0–100), measured on premultiplied colour.
  • Effort fast | balanced | max and presets lossless, losslessMax, fast, web, pixelArt, photo, smallest.
  • Full PNG decoder (all colour types and bit depths, Adam7, tRNS, CRC checks) and encoder; APNG input is returned unchanged.
  • Metadata: strip, keep colour chunks (default) or keep all valid chunks.
  • Deterministic output, identical on the VM, dart2js and dart2wasm.
  • png_minifier command line: files and directories, --preset, --quality, --effort, --strategies, --in-place, --dry-run, --json.
• Tests on PngSuite, Kodak crops and Kenney tilemaps; golden hashes checked on the VM, Chrome (dart2js) and Chrome (dart2wasm); tool/benchmark.dart.