How to measure dimensions of region boundary plot?

Hello,

I have an image (from MATLab example) and I want to know the number of pixels in/dimensions of the green boundary. As according to the code, the green boundary is overlaid on the image and is not a part of the image, I am unable to calculate its length or the number of pixels it has.

BW = imread('blobs.png');
Calculate boundaries.

[B,L,N] = bwboundaries(BW);
Display object boundaries in red and hole boundaries in green.

imshow(BW); hold on;
for k=1:length(B),
   boundary = B{k};
   if(k > N)
     plot(boundary(:,2), boundary(:,1), 'g','LineWidth',2);
   else
     plot(boundary(:,2), boundary(:,1), 'r','LineWidth',2);
   end
end

I want to make the green boundary a part of the image so that I can count its number of pixels too. Or any other way to do just that (measure the length of the green region).

Please help me in this regard.

Regards.

Answer 1

[Image Analyst]

Just get the size of boundary in the loop:

numPixels(k) = size(boundary, 1); % Count rows.

[Mohsina Zafar]

Thank you. This is exactly what I needed.

[Antonio Morales]

How could it be possible to get the area of the detected boundary? I am particularly interested in calculating the area to length ratio of all detected boundaries.

Thanks

[Image Analyst]

Use polyarea(x, y)

area = polyarea(x, y);