CMYK Overprinting and Knockout in Ghostscript

Question

I\'m trying to get a grasp on the capabilities of the current version of Ghostscript (see also this question that I asked a few days ago). So, I downloaded a \"test form\" for t

Answer 1

First answer is stop trying to use the X11 device, its an RGB device and not hugely well supported. In order to do X11CMYK the input must be rendered to CMYK then post filtered to RGB. Its not a good solution.

Overprinting is only defined for CMYK process colours (and spots), any other colour model will not perform overprinting. So I would suggest you render to TIFF or JPEG devices using their CMYK variants.

Spot colours are even more complex, if the device does not support the requested spot colour then it uses the tint transform to convert into the defined alternate colour space. If tint transformation takes place the spot is not overprinted.

Since the display devices cannot support spot colours, you can't preview spot overprinting using a display device. If you want to do this you should use the tiffsep device.

If you believe you have found a bug in Ghostscript, then please report it as such, but you will have to report it against a CMYK device, and I'll say now that we won't be very active with bugs in the X11 CMYK device, its practically unused.

Printing to an inkjet device depends on the printing workflow, and I have no idea what you are using for that. If its CUPS (and I'm guessing solely based on the fact that you are using an X11 device) then this 'should' just work. But it depends on the complete end-to-end print process, and I have no idea what it is you are doing.

Again note that spot colours will not be available on a CMYK printer, so overprinting spots is probably not going to work the way you expect.