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

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!!

[Jonas]

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]

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!!

Answer 1

[Image Analyst]

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)

[kanika bhalla]

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!!

Answer 2

[Stephan]

Same as in your question yesterday: regionprops will solve both problems in 1 line of code.

[kanika bhalla]

Hi Stepahn,

Thank you very much for your answer.

I was looking into doc regionprops. But unable to understand which property will suit in my case. Could you please elaborate more on this. I am really thank ful to you.

[Stephan]

https://de.mathworks.com/help/images/ref/regionprops.html#buoixjn-1-properties

In your case 'basic' should be helpful - this gives the centroid and the area

[kanika bhalla]

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!!