Find intersecting points in a image

How can I extract the boundary points of the first image. How can I plot it? How can I fiit a polynomical on the image boundary?

In the bottom image, after fitting a polynomial on the image boundary how an I find the intersecting points of the line and fitted polynomial ?

Answer 1

[KSSV]

I = imread('myimage') ;  % give your image 
[y,x] = find(I==0) ;     % white pixel value; 
idx = boundary(x,y) ; 
bnd = [x(idx) y(idx)] ;  % boundary points data 

Now you have boundary data points in hand. Make your line for which you want to get the intersection points with boundary. And then use https://in.mathworks.com/matlabcentral/fileexchange/22441-curve-intersections

Also there are other ways to get the intersection points without using the above. Read about knnsearch.

[mathru]

While running the code using your commands, getting the following error:

Index in position 2 exceeds array bounds (must not exceed 2).