Distances between regions in matlab

I am trying to find the distance between two points for different regions. However in order to get from one region to another there is a given point on the boundary between the two regions where you would go from point 1 to the boundary point to point 2. My problem is there are 8 different regions. So if point 1 is in region 1 and point 2 is in region 8 I may have to find the distance between point 1 to boundary point 1 to boundary point 2 etc. to point 8. The explanation here may be bad but I thought id give it a shot.

Answer 1

[Image Analyst]

Why don't you just go between the centroids of the regions?

There are other definitions of distances. It sounds like you'd better take a look at the Hausdorf distance to see if that's what you need: http://cgm.cs.mcgill.ca/~godfried/teaching/cg-projects/98/normand/main.html

[Zaid B]

Hi , do you have the matlab code for this ..please?

[Image Analyst]

@Zaid B, see my Image Segmentation Tutorial for a full demo:

Image Analyst's File Exchange

In short:

% Get centroids of all regions:
props = regionprops(mask, 'Centroid');
% Get a list of (x,y) centroids - each centroid in one row
xyCentroids = vertcat(props.Centroid);
x = xyCentroids(:, 1);
y = xyCentroids(:, 2);
% Get distances between every centroid and every other centroid:
distanceMatrix = pdist2(xyCentroids, xyCentroids);
% Just so we know what blob has what label, 
% let's label them in the overlay above the image.
hold on;
for k = 1 : length(x)
    plot(x(k), y(k), 'r+', 'MarkerSize', 40);
    str = sprintf('  %d = (%.1f, %.1f)', k, x(k), y(k));
    text(x(k), y(k), str, 'Color', 'r', 'FontSize', 15, 'FontWeight', 'bold');
end
hold off;