Question

Matlab code(well commented): Develop an Algorithm to generate a histogram by counting the different intensity levels. Use your algorithm with the image and compare to results to the 'imhist()' command results on the image.

Answer 1

1) Without IMHIST Function:

I=imread('pout.tif');   % Reading Image

[r,c]=size(I)          

n=r*c;                  % Total Pixels

x=1:256;

y=x';

G=imhist(I);            % G contains number of pixels at each

                          Intensity

cdf=cumsum(G);

cdfmin=min(cdf);

for i=1:256

h(i)= round(((cdf(i)-cdfmin)/(n-1))*255); %equalized pixel

                                           intensities                             

end

T=[y,G,cdf,h'];         % to generate table

new_image = zeros(r,c); % creating New Image matrix

new_image = uint8(new_image);

for i=1:r

     for j=1:c

               new_image(i,j) = h(I(i,j)+1);

     end

end

subplot(2,2,1);imshow(I);title('original image');

subplot(2,2,2);imhist(I);title('histogram of original image');

subplot(2,2,3);imshow(new_image);title('equalized image');

subplot(2,2,4);imhist(new_image);title('histogram of Eq. Image’);