Grouping object with minimum in-between distance.

Hi there I have a binary image with different objects. I want to fill the objects which are placed in a group with minimum in between distances (object 1,2,3,4 and 5 are in group). How can I avoid filling the other objects which are not in the group. Thank You

[Matthew Eicholtz]

What do you mean by "fill the objects which are placed in a group"? Do you mean that you want to fill the holes within individual members in a group? Or that you want to connect all members of a group by filling in the space between the objects?

[rupam baruah]

I want to fill the holes within individual members in a group.

Answer 1

[Matthew Eicholtz]

Use imfill with the form BW2 = IMFILL(BW,LOCATIONS) where LOCATIONS specifies the points at which to start the flood-fill operation.

Example

Create a sample image containing several shapes with holes:

I = zeros(200,200);

I = insertShape(I,'circle',[30 40 10],'LineWidth',10,'Color','w');
I = insertShape(I,'circle',[50 60 5],'LineWidth',2,'Color','w');
I = insertShape(I,'rectangle',[20 70 5 20],'LineWidth',2,'Color','w');

I = insertShape(I,'circle',[170 60 20],'LineWidth',5,'Color','w');
I = insertShape(I,'rectangle',[140 20 50 10],'LineWidth',5,'Color','w');
I = insertShape(I,'rectangle',[110 50 20 30],'LineWidth',2,'Color','w');

I = insertShape(I,'circle',[100 150 10],'LineWidth',8,'Color','w');
I = insertShape(I,'circle',[120 180 10],'LineWidth',6,'Color','w');
I = insertShape(I,'circle',[80 175 10],'LineWidth',4,'Color','w');
I = insertShape(I,'rectangle',[55 125 20 20],'LineWidth',10,'Color','w');

I = im2bw(I); %convert to binary image
figure; imshow(I);

Next, locate each object using bwconncomp and compute its centroid using regionprops.

cc = bwconncomp(I);
s = regionprops(cc,'Centroid');
xy = round(reshape([s(:).Centroid],2,[])'); %an n-by-2 array of object centroids
ind = sub2ind(size(I),xy(:,2),xy(:,1)); %linear indices of object centroids

Now I assume you have some method already for grouping objects together (e.g. clustering), so I won't describe how to do that. But, let's say that your algorithm determined that objects 4, 5, 6, and 7 should be grouped,

grp = [4 5 6 7];

Then, to fill in the objects in that group but not others, use imfill:

J = imfill(I,ind(grp));
figure; imshow(J);

NOTE: If one or more of the objects is non-convex or has multiple holes, you may need to seed the flood-fill algorithm with something other than the object centroid.

Hope this helps.