fill a particular blob with black

i segment and get a binary image with "n" number of blobs, Suppose i want to fill a particular blob with black and save it as image 2... how to do it...

for k = 4 : 4
        thisBlobsBoundingBox = blobMeasurements(k).BoundingBox;
        bw = labeledImage == k;
end

what should i do to the bw... please reply

Answer 1

[Takuji Fukumoto]

Please try this.

L = bwlabel(BW);
[r,c] = find(L == 4);
BW(r,c) = 0;
figure,imshow(BW)