How to count area under given surface ?

Hello,

I want to count areas limited by green lines.

So, for my image the result is three areas.

Can anyone help me please.

[darova]

do you have coordinates of green lines?

Answer 1

[Ameer Hamza]

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);

[MMSAAH]

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]

No, I meant maxk(): https://www.mathworks.com/help/releases/R2020a/matlab/ref/maxk.html. Are you using MATLAB release older than R2017b?

[MMSAAH]

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]

You will need to specify the pixel per cm to find out the area.