%CROP_BORDERS Crop the borders of an image or stack of images
%
% [B, vA, vB, bb_rel] = crop_borders(A, bcol, [padding])
%
%IN:
% A - HxWxCxN stack of images.
% bcol - Cx1 background colour vector.
% padding - scalar indicating how much padding to have in relation to
% the cropped-image-size (0<=padding<=1). Default: 0
%
%OUT:
% B - JxKxCxN cropped stack of images.
% vA - coordinates in A that contain the cropped image
% vB - coordinates in B where the cropped version of A is placed
% bb_rel - relative bounding box (used for eps-cropping)
% 06/03/15: Improved image cropping thanks to Oscar Hartogensis
function [A, vA, vB, bb_rel] = crop_borders(A, bcol, padding)
if nargin < 3
padding = 0;
end
[h, w, c, n] = size(A);
if isscalar(bcol)
bcol = bcol(ones(c, 1));
end
bail = false;
for l = 1:w
for a = 1:c
if ~all(col(A(:,l,a,:)) == bcol(a))
bail = true;
break;
end
end
if bail
break;
end
end
bcol = A(ceil(end/2),w,:,1);
bail = false;
for r = w:-1:l
for a = 1:c
if ~all(col(A(:,r,a,:)) == bcol(a))
bail = true;
break;
end
end
if bail
break;
end
end
bcol = A(1,ceil(end/2),:,1);
bail = false;
for t = 1:h
for a = 1:c
if ~all(col(A(t,:,a,:)) == bcol(a))
bail = true;
break;
end
end
if bail
break;
end
end
bcol = A(h,ceil(end/2),:,1);
bail = false;
for b = h:-1:t
for a = 1:c
if ~all(col(A(b,:,a,:)) == bcol(a))
bail = true;
break;
end
end
if bail
break;
end
end
% Crop the background, leaving one boundary pixel to avoid bleeding on resize
%v = [max(t-padding, 1) min(b+padding, h) max(l-padding, 1) min(r+padding, w)];
%A = A(v(1):v(2),v(3):v(4),:,:);
if padding == 0 % no padding
padding = 1;
elseif abs(padding) < 1 % pad value is a relative fraction of image size
padding = sign(padding)*round(mean([b-t r-l])*abs(padding)); % ADJUST PADDING
else % pad value is in units of 1/72" points
padding = round(padding); % fix cases of non-integer pad value
end
if padding > 0 % extra padding
% Create an empty image, containing the background color, that has the
% cropped image size plus the padded border
B = repmat(bcol,(b-t)+1+padding*2,(r-l)+1+padding*2);
% vA - coordinates in A that contain the cropped image
vA = [t b l r];
% vB - coordinates in B where the cropped version of A will be placed
vB = [padding+1, (b-t)+1+padding, padding+1, (r-l)+1+padding];
% Place the original image in the empty image
B(vB(1):vB(2), vB(3):vB(4), :) = A(vA(1):vA(2), vA(3):vA(4), :);
A = B;
else % extra cropping
vA = [t-padding b+padding l-padding r+padding];
A = A(vA(1):vA(2), vA(3):vA(4), :);
vB = [NaN NaN NaN NaN];
end
% For EPS cropping, determine the relative BoundingBox - bb_rel
bb_rel = [l-1 h-b-1 r+1 h-t+1]./[w h w h];
end
function A = col(A)
A = A(:);
end