how to display (3000x4000x4) matrix as image in matlab

I have created a 3000x4000x4 matrix in matlab, when I try to use image() function to display it as a picture, matlab told me image() function could only display m*n or m*n*3 matrix. So how could I display m*n*4 matrix as a picture? Many thanks.

[Matt J]

How are the 4 channels of the array meant to be interpreted? Are these CMYK images?

Answer 1

[Madheswaran]

Hi,

To display a 3000x4000x4 matrix as an image in MATLAB, it is essential to understand the representation of the four channels. Here's how you can handle two common scenarios:

If your matrix represents a CMYK image, you'll need to convert it to RGB format since the ‘image’ function does not support CMYK. Please note that converting CMYK to RGB may result in color shifts or potential inaccuracies in the color representation. Here is a simple MATLAB code that converts CMYK to RGB:

C = cmyk_image(:,:,1);
M = cmyk_image(:,:,2);
Y = cmyk_image(:,:,3);
K = cmyk_image(:,:,4);

R = 255 * (1-C/100) .* (1-K/100);
G = 255 * (1-M/100) .* (1-K/100);
B = 255 * (1-Y/100) .* (1-K/100);

rgb = cat(3, R, G, B);

Note the above code uses a simple formula that doesn't account for color profiles or advanced color management.

If your matrix is in RGBA format, where the fourth dimension represents alpha (transparency), you can display the image using the ‘AlphaData’ property:

rgb_image = rgba_image(:, :, 1:3);
alpha_data = rgba_image(:, :, 4);

image(rgb_image, 'AlphaData', alpha_data);

Note that transparent areas will appear in the default axes color, which is white. You can change the axes background color using the ‘Color’ property if needed.

If you would like to visualize the transparent areas of the image, you can use Image Manipulation Toolbox from file exchange as described in this answer: https://mathworks.com/matlabcentral/answers/1814745-i-have-an-image-that-is-234x432x4-size-wise-i-tried-imshow-and-image-but-it-doesn-t-work-what#answer_1064560

For more information, please refer to the following documentation: https://mathworks.com/help/matlab/ref/image.html