To find the smallest distance between a circle and an edge, given that you have already got the edge of the image, you may calculate the perpendicular distance between the center of the circle and the edge. Let this distance be 'a'.
The ability to automatically calculate the shortest distance from a point to a line is not available in MATLAB. To work around this, see the following function:
function d = point_to_line(pt, v1, v2)
a = v1 - v2;
b = pt - v2;
d = norm(cross(a,b)) / norm(a);
In this function, pt, v1, and v2 are the three-dimensional coordinates of the point, one vertex on the line, and a second vertex on the line, respectively. The following example illustrates how this function would be called:
v1 = [0,0,0];
v2 = [3,0,0];
pt = [0,5,0];
a = point_to_line(pt,v1,v2)
You may then subtract the radius of the circle 'r' from 'a' to get the shortest distance between the circumfrence of the circle and edge of the image.
DISCLAIMER: These are my own views and in no way depict those of MathWorks.
