[Image-SIG] Conversion from RGB to CMYK

Andrea Cappelli a.cappelli at asidev.com
Tue Jul 14 15:42:45 CEST 2009

Hi list,
I'm a beginner with Python and I'm using PIL to convert a lot of images
from RGB colorspace to CMYK in order to insert them in a catalogue to be
printed by a typography

i use the following piece of code

	handle = PIL.open(filePath).convert("CMYK")
	## some stuff

Everything seems ok, except than when I see the generated result (i
produce a pdf using reportlab) with Acrobat Pro the K layer of my images
is empty.

Every point of color in CMYK has the K value equal to 0. Seems that PIL
convert RGB to CMY, ignoring the K value. This is true except for black
images (RGB=0,0,0), that are mapped to (0,0,0,100)

I'm sure this behaviour doesn't depends on Reportlba because if I load
(with tha same code, trying to force colorspace to CMYK) images wich are
already in CMYK (so no conversion occur) the are displayed fine

This is a strange behaviour ora perhaps I'm wrong and I don't use
correctly PIL?

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