[Gimp-print-devel] Calculating actual Ink amounts from CMYK pipeline

[Walker B. <fo...@wa...>]

Dear Gutenprint community,

I’m at it again and doing some weird monochromatic toned printing with Gutenprint on an Epson P9000.

I’ve noticed something strange. If I build a CMYK profile and print a neutral target (gray ramp) that is converted to that profile with it through CMYK ink set in Gutenprint everything is correct.

If I print the same hard-encoded CMYK target four times through the printer by printing normal density of a single color per print (cyan at 1, MYK at 0, Magenta at 1 CYK at 0, etc) the print is entirely different with not enough black ink and too much color ink (in comparison).

There is some multiplication of numbers between the CMYK channels that is happening in the system at some point. Does anyone know what this multiplication is? If it’s a standard number/thing I can apply it to my backwards math.

warmest,
-Walker