Remove the gamma (gAMA) chunk from a PNG image to fix darker colors in IE

With the release of IE 7, the consistent use of PNG for Web sites and Web applications moved closer to a reality. However, while recently experimenting with a few concepts that rely heavily on PNG, I discovered IE interprets the gamma (gAMA) data chunk contained within a PNG differently than other browsers. The image will render darker, which can be problematic if you need a GIF or JPG to match the color profile of a PNG.

The W3C specification pinpoints the gamma and chromaticity data associated with a PNG as the primary advantage of this format, since it is a mechanism for more accurately managing colors across different platforms. Yet, it is the PNG alpha transparency that gives Web developers an opportunity to extend the design pallet. Unfortunately, in order to take advantage of one, it is necessary to compromise the other, and therefore, the gamma data should be removed.

TweakPNG is an amazing program for accomplishing this task. It is available under the GNU GPL, and is free to use. You can download it by clicking here. According to the Web site, the program has not been updated for a few years, but it works on Windows 95, 98, ME, 2000, and XP. Open up your PNG with TweakPNG, highlight the gAMA row under the Chunk column, right-click, and left-click on Delete. Now save the PNG, and the issue is resolved.

For more information on the PNG file format, visit the W3C specification page here:

http://www.w3.org/TR/PNG/

• Posted by Brian
• December 29th, 2006