Never mind,
The source of the error was the fact that in previous releases
we force tetrahedral interpolation for everything.
File cmsinterp.c:
Line 332
> cmsCalcCLUT16ParamsEx(nSamples, InputChan, OutputChan, FALSE, p);
---
< cmsCalcCLUT16ParamsEx(nSamples, InputChan, OutputChan, TRUE, p);
Isaac Case
Software Engineer
PCDT Color Workflow Team
Xerox Corporation
p 585.265.5472
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Case,
Isaac
Sent: Tuesday, May 20, 2008 1:42 PM
To: [email protected]
Subject: [Lcms-user] XYZ to CMYK differences lcms 1.15 vs 1.17
Hi,
I'm a software engineer with Xerox working with their color
scientists. Some of the work we do involves prototyping in matlab and
then implementing in C with lcms. We've been using lcms 1.15 for quite a
while now (with success I might add), but when we upgraded to 1.17 we
noticed some differences (with matlab and lcms 1.15).
This is not Image processing, but rather individual values being
passed through profiles.
Here's an example of one of our issues with 1.17 (in pseudocode
for clarity):
CMYK values -> CMYK ICC -> XYZ
XYZ -> CMYK ICC -> CMYK
The resulting CMYK values are inconsistent (1.15 vs 1.17) and
1.15 is closer to matlab
One example with data (all data as WORDs (16 bit unsigned) ):
1.15
CMYK (0,0,0,0) -> CMYK ICC A2B1-> XYZ (31588, 32760,27052)
XYZ(31588, 32760,27052) -> CMYK ICC B2A1 -> CMYK (29, 14, 0, 0)
1.17
CMYK (0,0,0,0) -> CMYK ICC A2B1-> XYZ (31588, 32760,27052)
XYZ(31588, 32760,27052) -> CMYK ICC B2A1 -> CMYK (59, 27, 16, 0)
MATLAB
CMYK (0,0,0,0) -> CMYK ICC A2B1 -> XYZ (31588, 32760, 27052)
XYZ(31588, 32760, 27052) -> CMYK ICC B2A1 -> CMYK (29, 11, 0, 0)
Matlab is not exactly the same as lcms, but, it is much closer to 1.15
than 1.17.
What happened between releases?
If more information is needed, please let me know.
Isaac Case
Software Engineer
PCDT Color Workflow Team
Xerox Corporation
p 585.265.5472
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