CMYK PDF to PDF color change

[Nik]

Hi All,

I'm and infrequent user of IM and most of the times I just use it to make thumbnails but my current project is to make a lowres CMYK PDF but I'm having problems with the output colour.

In its simplest form the command is:

convert input.pdf output.pdf

which gives me incorrect colour i.e. A red that has a CMYK value of:

0% cyan
100% Magenta
100% Yellow
0% black

is being converted too:

0% cyan
77% Magenta
83% Yellow
0% black

Could this be down to GhostScript? my full command is this:

Code: Select all

/usr/bin/convert -colorspace CMYK -profile "$iccProfilePath" -units PixelsPerInch -define pdf:use-trimbox=true -density 150 "$image1" -resize 2480x2480 -colorspace CMYK -profile "$iccProfilePath" -compress jpeg "$lowRes"

I'm running version 6.8..6-8 of IM on CentOS 6.4.

[fmw42]

probably best if you can post a link to your input PDF. You can upload to some free hosting service such as dropbox.com and put the link here.

Note that IM is not a very good system for going vector to vector. See http://www.imagemagick.org/Usage/formats/#vector


Also in this case what version of Ghostscript.

[Nik]

Hi Fred,

Thanks for your response

the source PDF can be found here:
https://www.dropbox.com/s/l3mpdvwrrc11z ... e.pdf?dl=0

the output PDf can be found here:
https://www.dropbox.com/s/0niiclpxfi4s7 ... R.pdf?dl=0

The version of GS is 8.70. If I remember correctly they where installed using Yum and those specific versions where installed for a reason that escapes me now!

Both raster and vector objects appear to have been affected by the conversion.

I did read something before posting that am xml delegate could be edited to make GS use a specific profile when converting but I've been on so many pages today I can't find that now either!

Many Thanks,
Nik

[fmw42]

I cannot get a perfect match, but these two are better than yours. The second is the closest. I convert to sRGB and then use a profile to convert back to CMYK.

Code: Select all

convert -density 150 Example_File.pdf -compress jpeg tmp3.pdf

http://www.fmwconcepts.com/misc_tests/cmyk_pdf/tmp3.pdf

Code: Select all

convert -density 150 -colorspace sRGB Example_File.pdf \
-profile /Users/fred/images/profiles/sRGB.icc -profile \
/Users/fred/images/profiles/USWebCoatedSWOP.icc \
-compress jpeg tmp4.pdf

http://www.fmwconcepts.com/misc_tests/cmyk_pdf/tmp4.pdf


I am using IM 6.8.9.8 Q16 Mac OSX
GS 9.10

[Nik]

Hi Fred,

thanks for your feedback and I can see that your second result is a lot closer than mine.

IM seems to be having problems with profiles though. I ran the below:

Code: Select all

convert -density 150 -colorspace sRGB '/home/imageuser/Desktop/Populate_Input/32-14-125-TRIAL-TRR.pdf' -profile '/home/imageuser/Desktop/ColorProfiles/AdobeRGB1998.icc' -profile '/home/imageuser/Desktop/ColorProfiles/CoatedFOGRA39.icc' -compress jpeg '/home/imageuser/Desktop/Populate_Input/tmp8.pdf' 

and got this feedback:

Code: Select all

convert: associate profile with image, a source and destination color profile required for transform `icc' @ profile.c/ProfileImage/812.
convert: Color profile operates on another colorspace `icc' @ profile.c/ProfileImage/1024

Does this mean anything to you?

Thanks,
Nik

[Nik]

Hi Fred,

I have found a solution to my colour issues and that is to bypass IM and just use ghostscript! The below code gives me a lowres PDF with the colours correct and keeps the vectors as vectors:

Code: Select all

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sProcessColorModel=DeviceCMYK -sOutputFile="$lowRes" "$image1"

Only time will tell if GS struggles with an other vector based elements that are introduced, but for now this seems to do the trick.

Thanks for your help,
Nik