Zopfli Optimization – Free Bandwidth (2016)(blog.codinghorror.com)
blog.codinghorror.com
Zopfli Optimization – Free Bandwidth (2016)
https://blog.codinghorror.com/zopfli-optimization-literally-free-bandwidth/
https://blog.codinghorror.com/zopfli-optimization-literally-free-bandwidth/
For 2-color scanned images, reducing the palette to 2, and zopfli combined is usually 1/7th the size of the original tiff or smaller as an optimized png. I've gotten similar results with many drawing based png as well.