MATLAB: Converting CMYK JPG to RGB JPG

cmykcolor spaceconversionimage processingImage Processing Toolboxmakecformmakeform

So if I detect a CMYK image I have a script written that attempts to convert the image to an RGB image so I can use imread on it (CMYK is not supported by imread for jpgs) and then tries to sharpen the image and convert it to black and white. Unfortunately the way I'm using applycform is not working and I keep getting an error that says "Cform structure is invalid for Named Color". Does anyone know anyway I might be able to resolve this or convert detect CMYK images to RGB images? All the Best!
 inprof = iccread('USSheetfedCoated.icc');
outprof = iccread('sRGB.icm');
C = makecform('icc',inprof,outprof);
for i=1:numFiles2
    info=imfinfo(fullfile(workingDirectory,imageFiles2(i).name));
    if info.ColorType == 'CMYK'
    fullfile(workingDirectory,imageFiles2(i).name) = applycform(fullfile(workingDirectory,imageFiles2(i).name),C);
    end
    frame = imread(fullfile(workingDirectory,imageFiles2(i).name));
    frame = imsharpen(frame);
    gray = rgb2gray(frame);
    imwrite(gray,imageFiles2(i).name);
  end

Best Answer

Hi Jacob, the first input to the 'applycform' function needs to be a matrix of the image data, rather than the path to the file itself. You are passing in a character vector for that argument, so the function assumes that you are using a named color profile, and errors out accordingly since the encoding 'C' from 'makecform' does not match.
Since 'imread' does not support CMYK JPG files in the first place, this puts us in a tricky situation. What you really need to do, is perform the conversion before being able to work with it at all in MATLAB. There are third-party tools that would allow you to do this conversion.
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