Colour Reduction

[djgrant1978]

Hi,

I'm attempting to convert a source RGB image to CMYK for use in a commercial printing press. The output profile (coldset) has a ink density of 260%, but when images are output through convert, the ink density is reduced to 192%, which means it is failing quality control.

I'm using the following command:

Code: Select all

convert -sampling-factor 1x1 profile AdobeRGB1998.icc input.jpg -quality 100 -profile coldset.icm output.jpg -colorspace CMYK

All help appreciated!

David

[magick]

Did you try setting the -black-point-compensation option?

[djgrant1978]

Thanks for the suggestion.

I've just tried using -black-point-compensation, but unfortunately the ink density remains at 192%.

[magick]

Type

• idenitfy -list configure

Does the DELEGATES or LIBS tag include lcms?

[djgrant1978]

Yes, lcms is mentioned in the LIBS section.

[magick]

To investigate further send a private-message with a URL to your input images and color profiles. Also tells us how to identify that the ink density is not what you expect. Are you talking about total-ink-density?

[magick]

We tried your command converting to JPEG and got the expected 260% total ink density. We're using ImageMagick 6.3.5-4 with LCMS version 1-16.

[djgrant1978]

I'm running Little CMS 1.16 too, but this is my IM version string (from identify -version):

Version: ImageMagick 6.3.2 03/04/07 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2007 ImageMagick Studio LLC

Is this colour adjustment a known issue in versions prior to 6.3.5-4? If so, can you tell me what version it was fixed in, so I can see if it's packaged for my environment?

Did you run the command verbatim?

[magick]

Color adjustment is not a known issue that we are aware of so we're not sure why ImageMagick 6.3.2 does not produce a proper total ink density for you.

[djgrant1978]

IM has been upgraded to version 6.3.3, and I now have total ink density of 260%.

Thank you very much for your help.