MATLAB: Better code to crop out a connected component

bounding boxconnected componentcropefficientregionprops

Hi, I have written this code to crop out just a connected component on an image:

rp = regionprops(cc, 'BoundingBox');
minr = rp(stainid).BoundingBox(2);
minc = rp(stainid).BoundingBox(1);
maxr = rp(stainid).BoundingBox(2) + rp(stainid).BoundingBox(4);
maxc = rp(stainid).BoundingBox(1) + rp(stainid).BoundingBox(3);
imstainzoom = im(minr:maxr, minc:maxc);

It works, but isn't the best code possible. Also, the bounding box returns non-integers (why is that?). Is there a much more efficient way to do this?

Best Answer

See my image segmentation tutorial where I crop out objects using their bounding boxes. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

I believe it gives coordinates on the half pixel to eliminate any ambiguity about whether the bounding box is the inclusive box, or one pixel layer outside that. So you can use ceil() and floor() to make it do it either way depending on what you prefer.

Related Solutions

MATLAB: Bounding Box largest rectangle

stats is a structure array. Each element is a structure and has it's own bounding box. So stats(1).BoundingBox is the bounding box (x,y,width,height) of the first blob. And stats(2).BoundingBox is the bounding box (x,y,width,height) of the second blob, and so on. To display them all:

hold on;
for k = 1 : length(stats) % Loop through all blobs.
  % Find the bounding box of each blob.
  thisBlobsBoundingBox = stats(k).BoundingBox;  
  rectangle('Position', thisBlobsBoundingBox);
end

MATLAB: Extraction of rectangular blob from binary image

How about comparing length around the blob and length around the bounding box of the blob, like:

% sample blogs
I = imread('pillsetc.png');
Iblob = rgb2gray(I) > 200;
% measure perimeter and bounding box for each blob
stats = regionprops(Iblob,{'BoundingBox','perimeter'});
stats = struct2table(stats);
% extract the blob whose perimeter is close to round length of its bounding box
stats.Ratio = 2*sum(stats.BoundingBox(:,3:4),2)./stats.Perimeter;
idx = abs(1 - stats.Ratio) < 0.1;
stats(~idx,:) = [];
% show the result
imshow(Iblob);
hold on
for kk = 1:height(stats)
  rectangle('Position', stats.BoundingBox(kk,:),...
      'LineWidth',    3,...
      'EdgeColor',    'g',...
      'LineStyle',    ':');
end

Best Answer

Related Solutions

MATLAB: Bounding Box largest rectangle

MATLAB: Extraction of rectangular blob from binary image

Related Question