Posted: 2006-04-17T07:11:15-07:00
The proper way to convert RGBA to CMYK is with two color profiles (e.g. sRGB & SWOP). The alpha channel should automatically be carried forward during the conversion. If not, try upgrading your version of ImageMagick and see if that fixes the problem. The current version of ImageMagick is 6.2.7-0.