Thanh Han The wrote:
I am not sure what can be done with this, since it's hard to define the right behaviour of pdftex in this situation. My vote is to leave things as they are, and document relevant issues in the manual.
I'm with Thanh, when it comes to the actual behaviour of the program. I do not see how pdftex could distinguish between a user who is knowledgeable and purposely trying to achieve a special effect and a user who is naively doing something redundant. In the case of CMYK image files, the probability of dealing with an expert user is pretty high, so the current action seems fine to me. That said, the behaviour should be documented, and perhaps even a warning could be issued if the /Decode in the image does not agree with the PDF default value? Best, Taco