Gerhard Fuernkranz wrote:
FYI, below is an example for the mentioned problem.
The example is CMYK. I also tried a RGB profile - and here I did not see the problem (B2A0 maps black to RGB=0)
Unfortunately I don't have your dataset, so I can't really reproduce this. If I try and duplicate this using a dataset I have (cromalin proof), I don't see the problem:
profile -v -qm -r1 -c3 -d0 -l250 -kh -S sRGB.icm test
iccdump -v3 -t bkpt test.icm XYZArray:Channels = 3 No. elements = 1= 9 0: 0.015549, 0.014771, 0.015457 [Lab 12.461413, 3.643509, -4.050391]
xicclu -ip -fb -pl test.icm 0 0 0 0.000000 0.000000 0.000000 [Lab] -> Lut -> 0.360593 0.000000 0.999295 0.995774 [CMYK]
xicclu -ia -ff -pl test.icm (Note it should be -ia to be comparable with the bkpt, which is an absolute value)
360593 0.000000 0.999295 0.995774 360593 0.000000 0.999295 0.995774 [CMYK] -> Lut -> 13.176778 0.069794 -0.790074 [Lab]
Which seems about right given that we've asked for the darkest neutral point, while the black point is the darkest, not necessarily neutral point. The difference between the two will depend on the how white the white point is on the device, and also how black the source profile black point is (I think).
Note for absolute:
Graeme Gill.