counting pixel in contour function.

Hi all,

I need to calculate the number of pixels of the long path (the blue one) obtained by a contour function, in order to calculate its length. I think a lot but got no solution

Answer 1

[DGM]

If you're trying to find the length of the curve defined by a set of xy coordinates, one way would be to do:

% a binary image
inpict = imread('cmantifmk.png');
inpict = inpict>128;

xy = bwtraceboundary(inpict,[41 50],'e'); % get xy coordinates
D = diff(xy,1,1); % point differences
D = sum(hypot(D(:,1),D(:,2))) % total euclidean distance

D = 871.8864

This is the sum of the distances between the centers of neighboring pixels in the boundary curve. This value will tend to be different than the results calculated by counting pixels or by using regionprops(...,'perimeter'). If you want to use regionprops(), you can look at the docs and decide which best suits your needs.

[ZEYAD ABDELBADIE MOHAMED ABDOU ZAHRAN -]

yes, i am trying to find the length of the curve, but only the lower part (the blue curve), i used the way you proposed, but the distance sum up to zero.

[Walter Roberson]

threshold, trace boundary, disconnect boundary at the extreme left and extreme right, calculate length of each of the two resulting curves, take the longer ?

[ZEYAD ABDELBADIE MOHAMED ABDOU ZAHRAN -]

thanks alot, it worked, but insted of using xy in the diff funcition, i used the defined contour (intcont)