The problem could be that you have an input file with a color profile ("ISO Coated v2 300% (ECI)"). The PDF still has the JPG with this color profile, but a PDF viewer won't access the profile this way. And ImageMagick creates the PDF 'only' with a general /DeviceCMYK colorspace. So, your original color profile is not used when the PDF has to be displayed in another colorspace (usually, "US Web Coated SWOP v2" is used as a general source color profile for CMYK data).
Some possibilities:
- You can access the correct CMYK data with Ghostscript. Example:
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gs -dSAFER -dBATCH -dNOPAUSE -dNOPROMPT -dMaxBitmap=500000000 -dAlignToPixels=0 -dGridFitTT=2 -sDEVICE=tiff32nc -dTextAlphaBits=4 -dGraphicsAlphaBits=4 -r254 -sOUTPUTFILE=pic1.tif pic.pdf
convert pic1.tif -profile "ISO Coated v2 300% (ECI).icc" -compress zip pic2.tif
The second IM command is just for assigning the correct color profile again.
- The PDF should display correctly in a program that allows you to set a CMYK working space - with your original color profile (probably with Acrobat).
- Or you could convert your CMYK image to "US Web Coated SWOP v2" first (if you have the profile). Example:
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convert pic.jpg -set units PixelsPerInch -set density 254 -profile USWebCoatedSWOP.icc +profile "icc,icm" -compress zip pic2.pdf
Not an ideal solution, but the PDF from ImageMagick should look ok (in every PDF viewer) after that.
For an even better solution, the PDF would have to be created with an /ICCBased object (where the color profile from the input image can be specified). I don't think that ImageMagick is able to do that.
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