Image processing: finding transfer function of histogram equalization
6 views (last 30 days)
Show older comments
Hello, lets say I have an image then I adjusted the contrast by using histogram equalization (histeq) Is there a way to plot or get an image of the transfer function that this command uses ?
0 Comments
Accepted Answer
Image Analyst
on 18 Nov 2013
Just take the histogram of the original image, then call cumsum on the pixel counts and plot it.
[pixelCounts, grayLevels] = imhist(grayImage);
cdf = cumsum(pixelCounts); % Make transfer function (look up table).
cdf = cdf / sum(cdf); % Normalize
plot(grayLevels, cdf, 'b-');
3 Comments
Image Analyst
on 3 May 2015
Huh? That has nothing to do with equalization, though equalization can use the cdf just like a lot of other functions do. This is just general purpose code that will compute the cdf regardless of your histogram. What do you mean by "other CDF"? What other CDF functions might there be?
More Answers (1)
Anand
on 18 Nov 2013
Or use the two argument syntax for histeq.
[histIm,T] = histeq(grayImage);
plot(T,'b-')
2 Comments
Image Analyst
on 18 Nov 2013
I didn't know it had that output - I guess I should have looked. Of course like I warn people histogram equalization gives a nonlinear stretch which usually looks pretty crummy and unnatural. imadjust() almost always gives a better looking image.
See Also
Categories
Find more on Histograms in Help Center and File Exchange
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!