Nice simple apps to optimize images for web or app development, that can be used by programmers and other people who don't know anything about image optimization...

Install these 2 little apps:

https://pngmini.com/

https://imageoptim.com/mac

And if you want to batch proces optimization, install the CLI tool:

https://github.com/JamieMason/ImageOptim-CLI

Another nice app for converting SVG to PNG:

http://gapplin.wolfrosch.com/