How to find out the different intensity values that are used in the image and make out a list of them.Then find the freq. of occurence (probability) of each of intensity values in the image?

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Anushka
Anushka 2015-7-30
回答： Image Analyst 2015-7-30
How to find out the different intensity values that are used in the image and make out a list of them. Then find the freq. of occurrence (probability) of each of intensity values in the image?

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Walter Roberson
Walter Roberson 2015-7-30
grayImage = rgb2gray(YourImage);
[unique_vals, ~, idx] = unique(grayImage(:));
counts = accumarray(idx(:), 1);
probs = counts ./ sum(counts);
bar(unique_vals, probs);

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Image Analyst
Image Analyst 2015-7-30
You can use
grayImage = rgb2gray(rgbImage);
[pixelCounts, grayLevels] = imhist(grayImage);
grayLevelFrequency = pixelCounts / numel(grayImage);
It depends on what you mean by intensity or how accurate you want to be. It would be best to calibrate your system using a Color Checker Chart and then convert to LAB and take the histogram of the L channel. This is what I do, and what John suggested above. If you just want to get an idea of graylevels for thresholding or something, then you don't need to go through all that.

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