Now, that’s pretty cool isn’t it? Well that is also where the problem lies when viewing PNG images in IE. This problem has long been blamed on Photoshop giving PNG images an incorrect gAMA chunk, but the problem only existed with Photoshop 5 and Photoshop 5.5. In other words, Photoshop no longer has this bug.

You see, IE doesn’t use a correct gamut setting, thus PNG images will appear darker; and back when Photoshop 5.0 and 5.5 gave incorrect gAMA chunks to PNG images it only aggravated the problem further. But since Adobe fixed the PNG gAMA chunk problem in Photoshop 6.0+, the current problem lies entirely with IE. But there is a way to do a short term fix for it.

There’s several PNG tools out there, but I use one called TweakPNG.
http://entropymine.com/jason/tweakpng/

To fix the gAMA problem simply remove the gAMA chunk altogether. Now PNG images will be displayed correctly in IE and still work in FF, NS, O, etc. Yet you can still take advantage of PNG alpha transparency and the smaller file sizes. Also consider removing cHRM, iCCP, and pHYs since they aren’t needed to display a PNG in a web browser either, and will make the final file size even smaller.

However, there is one major drawback. You can no longer take advantage of gAMA (well, duh). This means that if you made your design on a PC, it will look much brighter on a Mac, and if you made your design on a Mac, it will look much darker on a PC. Therefore it will act the same as a GIF or JPEG would, except you can still take advantage of Alpha Transparency and such. So just like a GIF made on a Mac will look darker on a PC, and a GIF made on a PC will look brighter on a Mac, thus PNG will now once again do the same.

It’s a no-win situation really. You could keep the gAMA chunk and just use CSS to put a 1*1px PNG image for your page and content backgrounds; that way your PNG images won’t look out of place in IE and still work on FF, NS, and O. But the problem is, of course, now your entire page will look slightly darker in IE then in FF, NS, or O. But at least it would all be in unison. If you do this you also don’t have to worry about your design looking too bright on a Mac if you designed it on a PC, or looking to dark on a PC if you designed it on a Mac.

Or, like I mentioned earlier, you could simply remove the gAMA chunk to make everything unison in all browsers again, except now, just like when you use GIF or JPEG, everything will look brighter on a Mac if you designed it on a PC, and darker on a PC if you designed it on a Mac. gAMA is one of the coolest features about PNG images so it’s a shame that it needs to be removed in order for a PNG to be displayed properly without using 1*1px PNGs for backgrounds and such.

My personal preference is to remove the gAMA chunk since most people that will view my websites use PCs (and therefore I don’t have to worry much about Mac users seeing something a lot brighter). There is talk that the final version of IE7 that will be shipped with Windows Vista will have the gAMA bug fixed (and therefore the whole PNG problem will be over once and for all since IE7 finally supports Alpha Transparency). But as of yet the beta version of IE7 doesn’t have the gAMA problem fixed, so I guess we’ll just have to see.

I noticed this effect comparing IE/firefox and thought at first I was going mad… i’m SURE i got the old colour-picker to that graphic and made the background the same colour…

http://hsivonen.iki.fi/png-gamma/