Histograms for image processing

Hi, I need some explanation for the following code we wrote in class today:

function [imageMapped] = L1_image_map(image,T)
imageMapped = zeros(size(image));
for channel = 1:size(image,3)
    for ii= 1:size(image,1)
        for jj=1:size(image,2)

              imageMapped(ii,jj, channel)=T(image(ii,jj,channel) +1,channel);
          end
          imageMapped = im2uint8(imageMapped);
      end
  end

end

Where T is the transformation function T=255*CDF. Thanks!

Answer 1

[Image Analyst]

Why should there be T=255*CDF? You'd use the CDF to create T if you were doing a histogram equalization, but this function doesn't do that (unless you passed in a T of that).

This code is basically a look up table operation, the kind of thing done by the function intlut(). It changes the gray level of the image based on what the value is in the index of T. For example if T(5) is 100, then a gray level of 4 would get mapped/changed to a gray level of 100.

1. T(1) is the new gray level for pixels with a value of 0.
2. T(2) is the new gray level for pixels with a value of 1.
3. T(3) is the new gray level for pixels with a value of 2.
4. etc.