ImageBoss is an API that brings all web development best practices for images to your clients. On demand CONTENT AWARE image resizing and cropping, progressive scans, compression and CDN to all your images by default.
Crunch is a free, open source macOS GUI application that is built on pngquant and zopflipng PNG image optimization. It uses a lossy approach to PNG image optimization. The tool is available through Homebrew as a native macOS application.
`$ brew cask install crunch`
Image examples + compression ratio analysis available on the Github repository README.