Converting CMYK JPG to RGB JPG

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

Answer 1

[Carl]

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.

[Jacob Mevorach]

Disappointing, but I appreciate that I know what I'll need to do now. Thanks!

[Walter Roberson]

Note: imread() does support CMYK Tiff images.

[Soan Duong]

Hi @Carl, I would like to design an end-to-end application in MATLAB. The input of the application is an image, which could be a JPEG image with CMYK colorspace. I did search the MATLAB function for reading the CMYK JPEG images but failed.

From your answer, I understand that MATLAB does not support reading CMYK JPEG image, but I wonder whether the new version of MATLAB supports reading? If so, could you please let me know the function. Any help you have to offer would be highly appreciated :).

[Image Analyst]

Why do you think the image is CMYK? What program created it?

[Soan Duong]

Hi @Image Analyst, I used the imfinfo() function to read the information of my image. The ColorType is CMYK.

Besides, when I read the image by imread() function, and I got an error of JPEG images with CMYK colorspace are not currently supported.

The two reasons make me think the image is CMYK. I just receive images and do not know what program created them.

[Abdurrahman Tosun]

it is very easy to save this position. save to your image at paint program, after that convert to jpeg again by using paint program :) if this save you please let me know