pngquant - Man Page

PNG converter and lossy image compressor

Examples (TL;DR)

Compress a specific PNG as much as possible and write result to a new file: pngquant path/to/file.png
Compress a specific PNG and override original: pngquant --ext .png --force path/to/file.png
Try to compress a specific PNG with custom quality (skip if below the min value): pngquant --quality 0-100 path/to/file.png
Compress a specific PNG with the number of colors reduced to 64: pngquant 64 path/to/file.png
Compress a specific PNG and skip if the file is larger than the original: pngquant --skip-if-larger path/to/file.png
Compress a specific PNG and remove metadata: pngquant --strip path/to/file.png
Compress a specific PNG and save it to the given path: pngquant path/to/file.png --output path/to/file.png
Compress a specific PNG and show progress: pngquant --verbose path/to/file.png

Synopsis

pngquant ⟨options⟩ [ncolors] file [file ...]

pngquant ⟨options⟩ [ncolors] - <file >file

pngquant converts 32-bit RGBA PNGs to 8-bit (or smaller) RGBA-palette PNGs, optionally using Floyd-Steinberg dithering. The output filename is the same as the input name except that it ends in ‘-fs8.png’ or ‘-or8.png’ (unless the input is stdin, in which case the quantized image will go to stdout). The default behavior if the output file exists is to skip the conversion; use --force to overwrite.

Options

-o out.png, --output out.png: Writes converted file to the given path. When this option is used only single input file is allowed.
--ext new.png: File extension (suffix) to use for output files instead of the default ‘-fs8.png’ or ‘-or8.png’.
-f, --force: Overwrite existing output files. “--ext .png --force” can be used to convert files in place (which is unsafe).
--nofs, --ordered: Disable Floyd-Steinberg dithering.
--floyd [=N]: Set dithering level using fractional number between 0 (none) and 1 (full, the default).
-s N, --speed N: 1 (brute-force) to 11 (fastest). The default is 3. Speed 10 has 5% lower quality, but is about 8 times faster than the default. Speed 11 disables dithering and lowers compression level.
-Q min-max, --quality min-max: min and max are numbers in range 0 (worst) to 100 (perfect), similar to JPEG. pngquant will use the least amount of colors required to meet or exceed the max quality. If conversion results in quality below the min quality the image won't be saved (or if outputting to stdin, 24-bit original will be output) and pngquant will exit with status code 99.
--skip-if-larger: If conversion results in a file larger than the original, the image won't be saved and pngquant will exit with status code 98. Additionally, file size gain must be greater than the amount of quality lost. If quality drops by 50%, it will expect 50% file size reduction to consider it worthwhile.
--posterize bits: Truncate number of least significant bits of color (per channel). Use this when image will be output on low-depth displays (e.g. 16-bit RGB). pngquant will make almost-opaque pixels fully opaque and will reduce amount of semi-transparent colors. When this option is enabled the default filename suffix is ‘-ie-fs8.png’ / ‘-ie-or8.png’.
--strip: Remove optional chunks (metadata) from PNG files.
--transbug: Workaround for readers that expect fully transparent color to be the last entry in the palette.
-v, --verbose: Enable verbose messages showing progress and information about input/output. Opposite is --quiet. Errors are output to stderr regardless of this option.
-V, --version: Display version on stdout and exit.
-h, --help: Display help and exit.