Here, your very own Blob remover:
function removeBlob
I = bwlabel(imfill(imread('coins.png')>100,'holes'));
h = imshow(label2rgb(I,jet(numel(unique(I(:)))),[0 0 0]));
set(h,'buttondownfcn',{@removeIt,I})
end
function removeIt(src,~,I)
cp = round(get(get(src,'parent'),'currentpoint'));
val = I(cp(3),cp(1));
I(I==val) = 0;
set(src,'cdata',bsxfun(@times,uint8(logical(I)),get(src,'cdata')));
end
