How to find the dark pixels in an image?

Question

Al Falamanki 2017-11-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/369663-how-to-find-the-dark-pixels-in-an-image

评论： Al Falamanki 2017-11-28

Hello. I have a lot of images like this one:

From the whole shrimp, I would like to determine the area of dark pixels as a percentage of the visible surface. Does anybody have an idea how to do that? My idea is to first define/find the desired color and then filter the image for that defined color.

Thanks Falamanki

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Answer 1

Bshara Murr 2017-11-28

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https://ww2.mathworks.cn/matlabcentral/answers/369663-how-to-find-the-dark-pixels-in-an-image#answer_293501

I = imread('shrimp.bmp');

N = I(:,:,3)>100;

I(:,:,2) = I(:,:,2)>100;

Where the second line treats each color channel separately, 3 represents the blue color, you can use 1 and 2 for red and green the 100 is the threshold that you can change as you with, you can use < as well, this gives you a bw image of the desired channel. the third line returns an rgb image but with a certain color channel thresholded but it will alter your white background as well.