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From: Dave Robinson on 15 Sep 2009 05:05
"Christophe " <Hagen_Cartoons(a)hotmail.com> wrote in message <h8md1u$8tr$1(a)fred.mathworks.com>...
> Thanks guys, but it does not resolve my problem.
> A bit of background might help: I am a scientist by day and freelance cartoonist by night and my agent has suddenly asked me to provide my cartoons in CMYK instead of RGB as the newspapers are asking for it now (after 10 years without a problem :( ). My problem is that my version of Paint Shop Pro does not do the RGB to CMYK conversion in one operation. It splits the files in 4 files and it is ugly...
> I thought about using Matlab to do a simple load, save as CMYK, voila...
> Unfortunately, what I wrote is:
>
> cartoon = imread('cartoon1401_colour.tif');
> Output_File_Name = 'cartoon1401_colour_CMYK';
> image(cartoon);
> axis off
> axis equal
> axis tight
>
> print('-dtiff','-cmyk','-r600',Output_File_Name);
> imfinfo('cartoon1401_colour_CMYK.tif')
>
> I was expecting the output to be CMYK as I specify the '-cmyk' flag, but the info from "imfinfo" says it is still RGB and this is what I don't understand:
>
> ans =
>
> Filename: 'cartoon1401_colour_CMYK.tif'
> FileModDate: '15-Sep-2009 07:30:14'
> FileSize: 21467516
> Format: 'tif'
> FormatVersion: []
> Width: 4804
> Height: 3602
> BitDepth: 24
> ColorType: 'truecolor'
> FormatSignature: [73 73 42 0]
> ByteOrder: 'little-endian'
> NewSubFileType: 0
> BitsPerSample: [8 8 8]
> Compression: 'PackBits'
> PhotometricInterpretation: 'RGB'
> StripOffsets: [3602x1 double]
> SamplesPerPixel: 3
> RowsPerStrip: 1
> StripByteCounts: [3602x1 double]
> XResolution: 600
> YResolution: 600
> ResolutionUnit: 'Inch'
> Colormap: []
> PlanarConfiguration: 'Chunky'
> TileWidth: []
> TileLength: []
> TileOffsets: []
> TileByteCounts: []
> Orientation: 1
> FillOrder: 1
> GrayResponseUnit: 0.0100
> MaxSampleValue: [255 255 255]
> MinSampleValue: 0
> Thresholding: 1
> ImageDescription: 'MATLAB Handle Graphics'
>
> Mayby, as you say, I should just bite the bullet and buy photoshop... It is a $1000 though :(

Have another word with your publisher - In my experience most printers want the image in the form of 4 monochrome image separations exactly as Paintshop Pro is giving you.

Remember that these separations cannot be viewed in a combined form directly on your monitor which only deals with a three plane image which is based on R,G and B pixels, not a 4 plane image. (You would need some form of display with cyan, magenta and yellow pixels. I believe such monitors are available for specialist applications).

You can simulate the printing press by converting your black (key) plane to equal quantities of cyan, magenta and yellow - then add this to the respective planes, then subtract the result from 1 (if you are working in doubles) or 255 (if you still are in uint8 format), then display as an RGB image. A bit of a long winded operation when Paintshop Pro will recombine your CMYK image back to RGB.

Hope that helps

Regards

Dave Robinson
From: Christophe on 16 Sep 2009 01:24
Thanks Dave...
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