How to calculate the area of only white part in the image

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I want to calculate the area of only white part as shown in the figure. I had used - bwarea(image). But I am not sure whether its calculating correct area or not. As I just need the white portion area.
Any help is much appreciated.
Thank you in advance!!
  2 Comments
Jonas
Jonas on 22 Apr 2021
you could count the white pixels, divide it by overall number of pixels and multiply it with the real size of the image
kanika bhalla
kanika bhalla on 22 Apr 2021
Hi Jonas,
Thank you for your answer. But I need some automatic way to calculate the area of white portion. Any help related to this is much appreciated.
Thank you!!

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Accepted Answer

Image Analyst
Image Analyst on 23 Apr 2021
You simply use nnz on your binary image to get the area in pixels
whiteArea = nnz(mask)
or you could use bwarea() - it uses a somewhat different algorithm for determining area (it's not just counting pixels).
whiteArea = bwarea(mask)
  1 Comment
kanika bhalla
kanika bhalla on 23 Apr 2021
Hi Image Analyst,
Thank you for introducing me to new function- nnz
As i have checked doc nnz. n = nnz(MASK). It returns the number of nonzero elements in matrix X. I have confusion then how it will calculate the area.
Now I have used bwarea() to calculate the area of white portion.
Thank you for your useful answers and help!!

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More Answers (1)

Stephan
Stephan on 22 Apr 2021
Edited: Stephan on 22 Apr 2021
Same as in your question yesterday: regionprops will solve both problems in 1 line of code.
  3 Comments
kanika bhalla
kanika bhalla on 23 Apr 2021
Hi Stephan,
Thank you for your help.
I tried what you guided me as shown below.
M=imread('C:\Users\Ucl\Desktop\test\mask_14H14\groundtruth_for_metrics\129groundtruth.jpg');
cc = bwconncomp(M);
stats = regionprops(cc,'Area');
But this is not giving me teh one desired output. Could you please guide me further why the output looks like this. I should get one area of only white portion.
Thank you!!

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