PNG optimisation tools

Question

A while back I used a PNG optimisation service called (I think) \"smush it\". You fed it a weblink and it returned a zip of all the PNG images with their filesizes nicely, w

Answer 1

I would question the wisdom of throwing away other chunks (like gAMA and iCCP), but if that's what you want to do it's fairly easy to use PyPNG to remove chunks:

#!/usr/bin/env python
import png
import sys

input=sys.stdin
out=sys.stdout

def critical_chunks(chunks):
    for type,data in chunks:
        if type[0].isupper():
            yield type,data

chunks = png.Reader(file=input).chunks()
png.write_chunks(out, critical_chunks(chunks))

the critical_chunks function is essentially filtering out all but the critical PNG chunks (the 4 letter type for a critical chunk starts with an uppercase letter).