MATLAB: Image patch extraction from given co-ordinate

digital image processingimage processing

Hello everyone, I have an image [800 x 900 x 4]. I have to extract patches with a center point [(x1,y1),(x2,y2)… ]. How can I do that ?.
Thanks

Best Answer

Your image is not 4D. It has 3 dimensions, unless what you posted in your question is not true.
patch{i}=IM(x(i)+[-8 8],y(i)+[-8 8],:);
This makes use of the quirk of Matlab that if you enter corner coordinates, it will return the entire square part.
For edge cases, the code below crops the part outside of the matrix (my comment below has a copy-and-past bug)
selected_patches = cell(length(x),1);
for i=1:length(x)
    xtemp=x(i)+[-8 8];
    xtemp(xtemp<1)=1;xtemp(xtemp>size(IM,1))=size(IM,1);
    ytemp=y(i)+[-8 8];
    ytemp(ytemp<1)=1;ytemp(ytemp>size(IM,2))=size(IM,2);
    selected_patches{i}=IM(xtemp,ytemp,:);
end
Related Question