How to use histogram equalization for a given image, without including the black background ?
I have images with no background (which i obtained via image masking) that I'm trying to upload on Matlab. However, Matlab keeps (automatically) adding a black background to my images. This poses a problem when I try to use histogram equalization, with the function histeq(), as the dark background seems to affect the process of color adjustment. Is there a way to use histogram equalization on the image itself without accounting for the background?
Prashant Kumar answered .
2025-11-20
To perform histogram equalization on an image while excluding the black background in MATLAB, you can follow these steps:
1. Read the Image:
Load the image into MATLAB.
img = imread('yourimage.webp');
2. Identify Non-Background Pixels:
Create a mask to identify non-background pixels. Assuming the black background has pixel value 0.
mask = img > 0;
3. Apply Histogram Equalization:
Perform histogram equalization on the non-background pixels.
equalized_img = img; % Copy the original image
equalized_img(mask) = histeq(img(mask));
4. Display the Result:
Visualize the original and equalized images.
subplot(1, 2, 1);
imshow(img);
title('Original Image');
subplot(1, 2, 2);
imshow(equalized_img);
title('Equalized Image');
This process enhances the contrast of the image while leaving the black background unchanged.