Script to recursively optimize all images in current directory

THIS WILL OVERWRITE YOUR ORIGINAL IMAGES AND STRIP METADATA. MAKE A SNAPSHOT.

Forked from this, which is a fork of: this

This will be POSIX sh compliant as soon as I fix the semaphore implementation.

Recommend also using Pingo but it appears to be closed source.

TODO:

• Pass shellcheck
• Use functions to make parallelization easier
• Don't reuse the same filenames so we can parallelize
• Use fd instead of find so walking files is a lot faster.
• Only use one fd or find and optimize both types of images in the same loop.
• Use file(1) to detect file type and skip empty files.
• Detect cpu count
• Only spawn N processes and make sure N are always running when there are images to optimize
• Detect if fd is installed and fall back to find if it isn't.
• Add support for gif and other file types
• Detect if the prerequisite programs are installed
• Install prerequisites if they are not installed