pngstrip (32bit, Windows Executable at 59 kb) is a small program I’ve written to strip out the various kinds of gamma and chromacity information from PNG files. It’s written in standard ANSI C, so should compile on anything reasonable, though it has only been tested on Windows XP. The source code is also freely available. It’s console program, just type out
pngstrip filename.png, and
filename.png will be stripped.
We spent years agonizing over the lack of 8-bit alpha channel in PNG in IE, and when we filly get it natively/nicely supported in IE they go and botch is so horribly.
Most of us have heard about gamma. But unless you do something in the graphics/print field, it mostly remains a button on our screen, where we tweak the luminocity of the screen. But of course, when an artist makes a snazzy PNG picture, making sure that it appears at the same display intensity as it did on his screen is understandably an laudarble goal. So PNG embeds gamma information, saying that this and that color, should be show at this and that intensity. The problem occurs when the BOG STANDARD (for 15 years and counting) HTML and CSS colors are NOT processed through the same system and thus don’t get the same gamma correction applied. The problem is easy to spot (need to be viewed in IE). The PNG files, once stripped, appears correctly.
I won’t really bother explaining this problem more, since it goes beyond stupid, I’ll just link further reading materials if you don’t know why you may wish to strip your PNG files for gamma information. Henri Sivonen has the best treatment on the topic.