Ghostscript - Wrong CMYK Color Conversion - 100% Yellow convert to 98% Yellow?

Question

I try to convert a CMYK .pdf as CMYK .tif with the good CMYK percentages.

But i've a strange color conversion.

Colors:

Look some converted color to understand the "strange" conversion:

100% yellow in pdf was converted as 98% yellow the TIF:

PDF = C:0 M:0 Y:100 K:0
TIF = C:0 M:0 Y:98  K:0

100% Magenta in pdf was converted as 1C/100M/1Y the TIF:

PDF = C:0 M:100 Y:0 K:0
TIF = C:1 M:100 Y:1  K:0

black is good (and all gray tone like 10%,20%...):

PDF = C:0 M:0 Y:0 K:100
TIF = C:0 M:0 Y:0  K:100

but full 100 is not good !?:

PDF = C:100 M:100 Y:100 K:100
TIF = C:73 M:68 Y:66  K:89

and a C100/M20 wrong too (pdf total 120 tif total 121 ?):

PDF = C:100 M:20 Y:0 K:0
TIF = C:99 M:21 Y:1  K:0

files:

download the source PDF: [https://drive.google.com/file/d/0Byc9qwtxxi1dSlo2eHJxM1hpMU0/view?usp=sharing][1]

download the converted TIF: [https://drive.google.com/file/d/0Byc9qwtxxi1dVWN6NWlBUEF0Z2c/view?usp=sharing][2]

!!!Attention: Open the files in photoshop to correctly preview the color and use the color picker to compare the value of each colors.

Cmd:

I search on google and read all the ghostscript doc since 2 weeks, and that's my best cmd :

gs -dNOPAUSE -dBATCH -dSAFER 
-sDEVICE=tiff32nc
-sDeviceNProfile 
-dKPreserve=2 
-dRenderIntent=1 
-dCOLORSCREEN=false 
-dNOINTERPOLATE 
-dUseCIEColor 
-dNOTRANSPARENCY 
-dGraphicsAlphaBits=4 
-dTextAlphaBits=4 
-dFirstPage=1 
-dLastPage=1 
-r600 
-sOutputICCProfile=USwebCoatedSOWPv2.icc 
-sOutputFile=CMYK.tif
CMYK.pdf

(Unix Ghostscript 9.10)

Doc:

http://www.ghostscript.com/doc/9.10/GS9_Color_Management.pdf http://ghostscript.com/doc/current/Devices.htm#PDF

???

What do you think ? is a bug or a wrong cmd !? Did anyone else have this experience?

Thanks,

UPDATE 1

I reduce the cmd at his minimal :

gs -dNOPAUSE -dBATCH -dSAFER 
-sDEVICE=tiffsep 
-dKPreserve=2 
-sOutputFile=CMYK.tif 
-r300 
-dGraphicsAlphaBits=4 
-dTextAlphaBits=4 
-dFirstPage=1 
-dLastPage=1 
CMYK.pdf

And have the same wrong color convertion.

For me, the ICC profile can't change color percents... a 100% Yellow is a 100% Yellow ! not agree? (in all cases, we have the same issue with or without icc profile)

UPDATE 2

At the beginning, i can't reproduce the colors "bug" in photoshop, I thought it was ghostscript.

But i found the difference between "assign" and "convert" icc profile in photoshop.

• photoshop "assign" screencast : http://quick.as/r2jrTn4zw
• photoshop "convert" screencast : http://quick.as/xQzaHZ9xp

And it is not a bug !

New issue

Can't we not use the icc profile when we convert a PDF to TIF ? or use globally the same profile to cancel the convert effect ?

Answer 1

First, update to the current shipping version of Ghostscript. If you still think you see a problem, then open a bug report at httpss://bugs.ghostscript.com

If you open a bug please be sure to attach the specimen file, and give a complete (as simple as possible) command line to reproduce the problem. If you are using an ICC profile, you'll need to supply that as well.

By the way, I think you have a typo there as well '-sOutputICCProfile=USwebCoatedSOWPv2.icc'

Oh, and if you are intending to get decent colour management, under no circumstances should you be setting -dUseCIEColor.

I'm not clear on what you expect the CMYK values to be when you are using an ICC Profile to correct the output, you surely aren't expecting them to be unchanged ?

Answer 2

I'm so close... with this tiny poorly documented option: -dNOSUBSTDEVICECOLORS

gs -sDEVICE=tiff 32nc -dNOSUBSTDEVICECOLORS -sOutputFile=CMYK.tif CMYK.pdf

In all of my test, the most uncatchable was the C100M100Y100K100... now is good like M100, K100, K50, M100C20, ... ! But only the Cyan100 and Yellow100 turn again on 99% !!!

I'll get it... on next...