Gamma Correction and Precision Color

• Transfer Functions and Gamma
• The gAMA Chunk
• Encoding Gamma
• Gamma Gotchas
• Chromaticity
• Color Management Systems and sRGB
• ICC Profiles

Anyone who has transferred images between a PC and a Macintosh--or even simply viewed on one platform an image created on another--has probably noticed one of the little gotchas of the computer world: images don't look the same on all systems. Images created on Macs tend to look too dark on PCs; images created on PCs tend to look too bright and washed out on Macs. A pure yellow on one machine may have an orange or greenish tint on another. Even on a single machine there are usually obvious changes in brightness and color as the monitor (CRT) warms up, not to mention when the user adjusts the screen controls. And in the absence of tedious calibration procedures and high-end color-conversion software, what comes out of the printer is, at best, only a vague approximation of what the screen shows.

PNG certainly doesn't solve all of these problems, but it does provide image authors with the means to minimize many of them, as long as the editing and viewing software is written properly. As recently proposed standards are approved and implemented in hardware, from graphics cards, to monitors, to printers and scanners, there is reason to expect that platform-independent color will become the norm, not the exception, in the new millennium.