What is the crowd's opinion of pngcrush?

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you can 'fix' that (by removing all the colour profile information) with a command line tool called 'pngcrush'. like so:

pngcrush -q -rem gAMA -rem cHRM -rem iCCP -rem sRGB oldfile.png newfile.png

i wrote a script to go through all the pngs in a folder and fix them (it also has the added bonus of reducing the file size a lot of the time).

#!/bin/bash

echo " " for file in ./*.png; do echo "Working on $file" pngcrush -q -rem gAMA -rem cHRM -rem iCCP -rem sRGB $file "$file.tmp" mv $file "$file.old" mv "$file.tmp" $file done echo " " echo "Complete." echo " "

# Remove old files rm -rf *.png.old

2D here- I use pngcrush as part of my build process. For a web-based game, combining images into a single big spritesheet can cut down on HTTP requests (assuming you have a lot of images). A lot of people like TexturePacker because its GUI-based, but I've also used spritesheet.js which does the same thing.

I would try converting them into CgBl PNGs, they often work better with iOS devices.

There's also pngcrush, but CgBl will get them a bit more 'apple optimized'

https://www.youtube.com/watch?v=TWEXCYQKyDc

tells you how people typically hide data.

http://pmt.sourceforge.net/pngcrush/

Will lossless optimize image files to a smaller size. Thus it gets ride of all the data that does not visually impact the file. That'll remove all basic level water marking. The video goes into other water marking so you'll have to check that out. It typically done with small variations in color. So inspect the image under your program of choice and you should be able to tell if there is some unusual data.

Once you've removed all meta data, its more or less a game of seeing if the image in abnormal in some way. Hopefully this not being a jpeg (being a jpeg, its already a somewhat chaotic looking static). With png and the likes just seem is its abnormal, or doesn't match up with other identical parts. (if you have two identical white sections of the picture, under closer inspection they should be completly the same data wise as well)

Check out Google Pagespeed, it's a Chrome (and I think FF) plugin that will help a bit:

http://code.google.com/speed/page-speed/

Use PNGCRUSH with the bruteforce option enabled to really cut down on image size (without quality loss).

Ok, I did some science for you (and because I was curious).

I took a high quality jpg and reduced it to a 100x66 png.

Original: 30,214 bytes.

Using PNG Crush: 22,682b (24.9% reduction)

Using PNGNQ (default 256 colors): 6,567b (78.3%)

Using PNGNQ, then PNG Crush: 5,694b (81.2%)

Using ImageAlpha (Median Cut, 64 colors): 4,047b (86.6%)

At 64 colors and at that size, the thumbnail looked pretty close to the original. You should be able to reduce the colors with pngnq, but it kept giving me an error.

EDIT:

I forgot I converted it to a jpg with quality of 40%: 20,465b