Matlab Tutorial : Digital Image Processing 5 - Histogram Equalization

Here is the input image which I got from wiki - Histogram equalization:

It's histogram looks like this:

img = imread('Hawkes_Bay_NZ.jpg');
imhist(img);

The Histogram Equalization algorithm enhances the contrast of images by transforming the values in an intensity image so that the histogram of the output image is approximately flat. See the picture below.

Picture source: wiki

img = imread('Hawkes_Bay_NZ.jpg');
figure, img_eq = histeq(img); imshow(img_eq);

The histogram after the histogram equalization:

img = imread('Hawkes_Bay_NZ.jpg');
imhist(histeq(img)); 

In this section, we'll use imadjust() and get similar effect of doing histogram equalization operation.

img = imread('Hawkes_Bay_NZ.jpg');
img_adj = imadjust(img, [0.4,0.86],[0.0,1.0]);
imshow(img_adj); 

img = imread('Hawkes_Bay_NZ.jpg');
img_adj = imadjust(img, [0.4,0.86],[0.0,1.0]);
figure;
hold on;
imhist(img);
imhist(img_adj);
hold off;