overlaying CMYK pure black object onto PNG image

[wfzimmerman]

Hi,

I am overlaying a bar code which must be in pure black (0,0,0,1 CMYK) on to a book cover which starts out in RGB. When I composite the bar code file onto the book cover canvas, something is causing the pure black to be converted to RGB blacks that are not pure black. The printer requires the book cover to be CMYK and the bar code in pure black. I can convert the RGB cover to CMYK successfully, but the bar code is no longer pure black. Any ideas what is happening here?

Fred

[fmw42]

IM cannot properly composite with CMYK colorspace, as far as I know.

You would be best to process everything in sRGB and then at the end convert to CMYK preferably with profiles (or -colorspace CMYK).