Hi John,
Welcome to color management world. As you have already discovered, things are more complex that it would seem on first try. Ok, fear not all we have been students and I know how bad is this feeling. Here are some clues, hope that helps, but still you need to do your homework to get them working. For doing a RGB to CMYK conversion, you have several options. First option is to use some sort of model. Many people uses models to convert to CMYK, mostly with little success. A very naive approach is to just do C=1-R; M=1-G; Y=1-B; and then extract K. This is theoretically ok, but in practice it does not work because CMY inks and ink interaction is more complex that this simple model. More sophisticated models may use Yule-Nielsen or Kubelka-Munk equations. That involve differential calculus. With those models you can approximate what real inks do, but to do that you need real-world measurements as well. Modern color management uses another approach which is completely measurement based. It stores a series of measurements and interpolates between them. For interpolation, trilinear or tetrahedral algorithms may be used. Those tables can be optimized by using non regular partitions, and this can be approximated by using a set of curves prior interpolation. So what you really need is to create 4 tables, one for each CMYK output channel. Each of those tables should be indexed by 3 dimensions, namely RGB channels. Then you can obtain CMYK by means of interpolation. Then, ICC is a file format that can be used to store measurements, but the ICC spec way too complex and I think far above what you need. My recommendation would be to first try to understand the 3D interpolation technology I just described. There is abundant literature on that. Once you could do a good RGB to CMYK by just using a single LUT, try to use linearization tables and non-uniform partitions. If you succeed on that, the problem is mostly solved. Good luck Marti Maria ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available. Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
