/usr/share/psychtoolbox-3/PsychOneliners/CropBlackEdges.m is in psychtoolbox-3-common 3.0.11.20131230.dfsg1-1build1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | function coords = CropBlackEdges(plaat)
% coords = croblackedges(image)
% returns coordinates that can be used to cut the black edges from an image
% the trick is to sum the image in the x-direction and find where the sum
% is zero, then you know where there are black edges above and below the
% image; same trick for the edges left and right by summing in the
% y-direction.
%
% COORDS = [xmin xmax ymin ymax]
%
% to cut the edges use:
% cutimage = image(coords(3):coords(4),coords(1):coords(2));
%
% DN 2007 Wrote it
% DN 2008-07-30 Now returns correct indices if one or more or all sides of
% the image do not have a black edge
% DN 2009-02-02 Now returns error msg if all is black
plaat = sum(plaat,3);
psychassert(any(plaat(:)),'No image in input matrix');
plaatx = sum(plaat,2);
plaaty = sum(plaat,1);
% y coordinates
qdiff = diff([plaatx])~=0;
if plaatx(1)~=0 && plaatx(end)~=0
coords(3) = 1;
coords(4) = size(plaat,1);
else
if plaatx(1)~=0
coords(3) = 1;
else
coords(3) = find(qdiff,1,'first')+1;
end
if plaatx(end)~=0
coords(4) = size(plaat,2);
else
coords(4) = find(qdiff,1,'last');
end
end
% x coordinates
qdiff = diff([plaaty])~=0;
if plaaty(1)~=0 && plaaty(end)~=0
coords(1) = 1;
coords(2) = size(plaat,2);
else
if plaaty(1)~=0
coords(1) = 1;
else
coords(1) = find(qdiff,1,'first')+1;
end
if plaaty(end)~=0
coords(2) = size(plaat,2);
else
coords(2) = find(qdiff,1,'last');
end
end
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