icnsoptim

icnsoptim is a macOS command line script to losslessly optimize Apple Icon (.icns) files. This is accomplished by disassembling the file, brute-force-optimizing the PNG images within using oxipng and then rebuilding the icon with createicns, a utility which doesn't bloat and tamper with the provided PNG files, unlike Apple's suboptimal iconutil.

Lossless compression results vary from file to file but are usually significant, typically around 20-50%. An experiment where optimization was performed on all icon files in the /Applications directory hierarchy resulted in an average ~30% reduction in size.

How to use

The repository contains the bash script imgoptim.sh, which optimizes icons via the command line. Use it thus:

bash icnsoptim.sh path/to/file.icns

This will create a new file named file-optimized.icns in the current working directory. In order to work, oxipng and createicns binaries need to be present in the same directory as the script. You can optionally specify the path to the output file:

$ bash icnsoptim.sh --help
Usage: icnsoptim.sh <input.icns> [output_path/output.icns]
  <input.icns>: Path to the .icns file to optimize.
  [output_path/output.icns]: Optional. Full path for the optimized .icns file.
                             If not provided, output will be <input_basename>-optimized.icns
                             in the current working directory.

BSD License

Copyright (C) 2025 Sveinbjorn Thordarson <sveinbjorn@sveinbjorn.org>

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.