Transform PNG files into the requisite sizes for Apple platforms. Doesn't require ImageMagick which can be a pain to get working on a Mac. Instead, it uses the sharp module.
--input input file
--output output directory
--spec list of images sizes to generate, see example below
npm install -g apple-icon-gen
apple-icon-gen --input='data/input/icon.png' --output='data/output' --spec='20@2 20@3 29@2 29@3 40@2 40@3 60
@2 60@3'
The code is really simple. Modify/debug it if there are exceptions.