How to count area under given surface ?

2020 4 30
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更新时间：2020 5 4
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Hello,
I want to count areas limited by green lines.
So, for my image the result is three areas.
Can anyone help me please.

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Ameer Hamza
Ameer Hamza 2020-4-30
编辑：Ameer Hamza 2020-4-30

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Try this. It gives the area of three regions in number of pixels
im = im2double(imread('area.jpeg'));
im(:,end-5:end,:) = 0; % remove the white line at right and bottom of image
im(end-5:end,:,:) = 0;
mask = (im(:,:,1)>0.75) & (im(:,:,2)>0.75) & (im(:,:,3)>0.75);
regions = bwconncomp(mask);
areas = cellfun(@(x) numel(x), regions.PixelIdxList);
required_areas = maxk(areas, 3);

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MMSAAH
MMSAAH 2020-5-3
Thank you for your reply.
For this line :
required_areas = maxk(areas, 3);
Did you mean ? max(areas, 3);
However, when running the above code, I get more than three values for the required area:
required_areas =
3 3 3 118 116 3 106
Could you please let me know how to correct it ?
Ameer Hamza
Ameer Hamza 2020-5-3
No, I meant maxk(): https://www.mathworks.com/help/releases/R2020a/matlab/ref/maxk.html. Are you using MATLAB release older than R2017b?
MMSAAH
MMSAAH 2020-5-4
I'm using R2016a.
I've changed maxk() by :
[val ind] = sort(areas,'descend');
required_areas=val(1:3);
Now, it works.
Is it possible to transform the number of pixels to cm ?
Ameer Hamza
Ameer Hamza 2020-5-4
You will need to specify the pixel per cm to find out the area.

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