Q. Why can't Windows Mobile support more than 65,536 colors like other mobile platforms can?

A. The Windows Mobile platform has long supported 65,536 colors, which is 16-bit color. Many mobile screens actually support four times that number of colors (262,144) and other mobile platforms support that many, so why doesn't Windows Mobile?

I researched this and came across a great blog by the Windows Mobile team that made a lot of sense. Check out the entry for a more in-depth answer, but the basics are below.

Most mobile platforms use a 32-bit processor, so dealing with 16-bit color works well. The processor can effectively process two pixels at a time on a 32-bit processor, because each pixel on screen is 16 bits. To support 262,144 colors, 18-bit color would have to be used, but that doesn't fit well on a 32-bit processor. With 18 bits, you consistently have extra bits being carried over into the next CPU computation to handle the extra 2 bits, which make processing very inefficient. Platforms that support 262,144 colors actually use 24-bit color, which is more CPU friendly, and just throw away 6 bits of information—which is a lot of wasted computation.

It's because of this inefficiency that the Windows Mobile platform recommends against more than 65,536 colors today. The computation hit just isn't worth it for the limited quality difference between 16-bit and 18-bit color. Once mobile screens support 24-bit color, you'll see Windows Mobile supporting 24-bit color, because there's no wasted computation and the quality difference is worth the extra processing.

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