A tool for lossy PNG image file optimization with python

Crunch

Crunch is a tool for lossy PNG image file optimization. It combines selective bit depth, color type, and color palette reduction with zopfli DEFLATE compression algorithm encoding using the pngquant and zopflipng PNG optimization tools. This approach leads to a significant file size gain relative to lossless approaches at the expense of a relatively modest decrease in image quality (see example images below).

Historical benchmarks with the files included in Cédric Louvrier's PNG Test Corpus versus other commonly used PNG optimization software are available in BENCHMARKS.md.

Crunch PNG image optimization is available through the following applications in this repository:

crunch - a *nix command line executable that can be used on macOS, Linux, and Windows POSIX application deployment environments such as Cygwin
Crunch GUI - a native macOS drag and drop GUI tool
Crunch Image(s) service - a macOS right-click menu service for PNG images selected in the Finder

Install and Usage

Install and usage documentation links for each of the Crunch applications are available below.

Examples

The following examples demonstrate the benefits and disadvantages of the current iteration of Crunch's aggressive space saving optimization strategy. In many cases, the PNG optimization minimizes file size with an imperceptible decrease in image quality. In some cases, degradation of image quality is visible. View the horizon line in the prairie photo below for a demonstration of an undesirable artifact that is introduced with image processing. Experiment with the image types that you use and please submit a report with examples of any images where the image quality falls short of expectations for production-ready files.