I am trying to write a function for the Gamma Correction, this is what I have so far. the problem is the intensities of the output image is either 0 or 255. what am I doing wrong?

function adjust_im= Gamma_c(im, y, c)
      rows = size(im,1);
      cols = size(im,2);
      mat= zeros(rows,cols,class(im));
      for r=1: rows
           for co=1: cols
               pixel = im(r,co);
               p1 = double(pixel/255);
               p2 = double(c*((double(p1))^y));
               p3 = double(p2*255);
               mat(r,co) = round(p3);
           end
     end
adjust_im= mat;

Answer 1

[Adam]

double(pixel/255)

will divide pixel by 255 then convert to a double. Assuming your image is an 8-bit integer data type this is not what you want as it will use integer division with truncation so everything apart from 255 will become 0. Use

pixel = double( im(r,co) );

or convert the whole image to double before the for loop (probably more efficient) and then you should not need all the other casts to double that you have.

[Reihaneh Khoshghadam]

I converted the whole image and it's working perfectly. thanks for the help.