Given a colour image whose light intensity is dim at the edges and bright in the middle, such as [dim bright dim], which computer vision technique would be recommended to correct this imbalance?

While I believe Histogram Equalisation could help, I've read that it also introduces an unrealistic look to an image by exaggerating the blue channel.

I consider implementing an image processor for this task.

1 Answer 1


One classic approach is using top hat filtering for leveling uneven illumination. You should perform morphological opening with a large structuring element, then remove the result from the original image.

If you have dark objects on light background you should do bottom hat filtering (dual of top hat filtering): subtract the closing with a large structuring element from the original image.

Result of top hat filtering

  • Thanks WebMonster. I'll take a look at this as I've never heard the name before. Does this approach work equally as well with coloured images as it does greyscale?
    – BlackBox
    Apr 30, 2014 at 19:30
  • I don't know if there is a generalization of morphological operators for colored images. You could convert the image to HSV color space, process the V channel as a grayscale image, then display the image. There will be some colour bleeding, but it could be good enough depending on your goals.
    – WebMonster
    Apr 30, 2014 at 20:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.