ImageOptim
ImageOptim is a GUI for lossless image optimization tools: Zopfli, PNGOUT, OxiPNG, AdvPNG, PNGCrush, JPEGOptim, Jpegtran, Guetzli, Gifsicle, SVGO, svgcleaner and MozJPEG.
Building
Requires:
git clone --recursive https://imageoptim.com ImageOptim
cd ImageOptim
To get started, open imageoptim/ImageOptim.xcodeproj. It will automatically download and build all subprojects when run in Xcode.
In case of build errors, these sometimes help:
git submodule update --init
cd gifsicle # or pngquant
make clean
make