function varargout = imregrotate(varargin)
%ROIROTATE Rotate & crop region of interest avoiding 'black corners'.
% B = ROIROTATE(A,ROI,ANGLE,METHOD) rotates the region of intererest ROI
% found in the image A by ANGLE degrees in a counter-clockwise direction,
% using the specified interpolation method and gives the rotated
% region as output in B cropped out of the original image.
%
% Usefulness
% ----------
% ROIROTATE was designed to avoid the 'black corners' typical of
% MATLAB's imrotate function, which are apearing from its behaviour
% of padding by zeros the space outside the image borders prior to
% the rotation. This is possible if the image to be rotated is
% part of a bigger image - which is the definition of a 'region
% of interest' -, because there is enough information to fill
% the corners.
%
% Description
% -----------
% Apart of the first entry which is based on the IMCROP syntax,
% all other are identical to the IMROTATE function.
%
% ROI is a four-element vector with the form [xmin ymin width height];
% these values are specified in spatial coordinates.
%
% xmin - starting pixel to be cut, x-th of the original image
% ymin - same on y-axis
% width - number of pixels to be cut minus one (width)
% height - same on height
%
% If you want to point the 5 pixel wide & 7 pixel heigh NW corner
% of an image, replace R with [1,1,4,6].
%
% Because ROI is specified in terms of spatial coordinates,
% the WIDTH and HEIGHT of ROI do not always correspond exactly
% with the size of the output image. For example, suppose ROI
% is [20 20 40 30], using the default spatial coordinate
% system. The upper left corner of the specified rectangle is
% the center of the pixel (20,20) and the lower right corner is
% the center of the pixel (50,60). The resulting output image
% is 31-by-41, not 30-by-40, because the output image includes
% all pixels in the input that are completely or partially
% enclosed by the rectangle.
%
% Note for IMCROP:
% To cut the NW pixel only:
% NWcornerPixel = imcrop(I, [1,1,0,0]);
%
% To cut the first top stripe of pixels:
% topStripe = imcrop(I, [1,1,size(I,2)-1,0]);
%
% METHOD is a string that can have one of these values:
%
% 'nearest' (default) nearest neighbor interpolation
% 'bilinear' bilinear interpolation
% 'bicubic' bicubic interpolation
%
% If you omit the METHOD argument, ROIROTATE uses the default
% method of 'nearest'.
%
% To rotate the image clockwise, specify a negative angle.
%
% Class Support
% -------------
% The input image can be of class uint8, uint16, or double.
% The output image is of the same class as the input image.
%
% Example
% -------
% I = imread('circuit.tif');
% J = imrotate(imcrop(I,[60 80 100 90]),-21,'bilinear','crop');
% [K x y w h] = roirotate(I,[60 80 100 90],-21,'bilinear');
% figure, subplot(1,3,1), imshow(I), title('roi')
% rectangle('Position',[60 80 100 90],'EdgeColor','red');
% rectangle('Position',[x y w h],'EdgeColor','green');
% subplot(1,3,2), imshow(J), title('imrotate')
% subplot(1,3,3), imshow(K), title('roirotate')
%
% See also IMROTATE, IMCROP, IMRESIZE, IMTRANSFORM, TFORMARRAY.
% Vlad Atanasiu - 06/05/2002
% Revisions: 3 > 01/11/2008
% check image input data
[A,dim,x,y,width,height,ang,method] = parseInputs(varargin{:});
% calculate padding borders
padX = abs(ceil(height*sin(ang*pi/180)/2));
padY = abs(ceil(width*sin(ang*pi/180)/2));
% padding zeros if extended region of interest coordinates outside image
if x-padX < 1 % left
A = [zeros(size(A,1),padX-x+1,dim) A];
end
if y-padY < 1 % top
A = [zeros(padY-y+1,size(A,2),dim);...
A];
end
if x+width+padX > size(A,2) % right
A = [A zeros(size(A,1),x+width+padX-size(A,2),dim)];
end
if y+height+padY > size(A,1) % bottom
A = [A;...
zeros(y+height+padY-size(A,1),size(A,2),dim)];
end
% cut extended region
ROI = imcrop(A,[x-padX y-padY width+padX*2 height+padY*2]);
% rotate extended region
ROI = imrotate(ROI,ang,method,'crop');
% cut region
varargout{1} = imcrop(ROI,[padX padY width height]);
% gives extended region coordinates
if nargout == 5
varargout{2} = x-padX;
varargout{3} = y-padY;
varargout{4} = width+padX*2;
varargout{5} = height+padY*2;
end
% ------------------------------------------------
function [A,dim,x,y,width,height,ang,method] = parseInputs(varargin)
% Input checkings
% Defaults
method = 'n';
% Check number of input parameters
error(nargchk(3,4,nargin));
switch nargin
case 3, % regrotate(A,reg,ang,)
A = varargin{1};
x = varargin{2}(1);
y = varargin{2}(2);
width = varargin{2}(3);
height = varargin{2}(4);
ang = varargin{3};
case 4, % regrotate(A,reg,ang,method)
A = varargin{1};
x = varargin{2}(1);
y = varargin{2}(2);
width = varargin{2}(3);
height = varargin{2}(4);
ang = varargin{3};
method = varargin{4};
otherwise,
error('Invalid number of input arguments.');
end
% Check validity of the input parameters
if ischar(method),
strings = {'nearest','bilinear','bicubic'};
idx = strmatch(lower(method),strings);
if isempty(idx),
error(sprintf('Unknown interpolation method: %s',method));
elseif length(idx)>1,
error(sprintf('Ambiguous interpolation method: %s',method));
else
method = strings{idx};
end
else
error('Interpolation method have to be a string.');
end
if size(varargin{2},2) ~= 4
error('Region of interest should be defined by 4 arguments.');
end
% transforms the format of A into an image if it is a filename
if (isstr(A))
A = imread(A);
end
% gets the dimensions of A
dim = ndims(A);
if dim == 2, dim=1; end
% modifies if needed the region of interest coordinates if outside image
if x < 1, x = 1; end
if y < 1, y = 1; end
if x > size(A,2)-1, x = size(A,2)-1; end
if y > size(A,1)-1, y = size(A,1)-1; end
if x+width > size(A,2)-1, width = size(A,2)-x-1; end
if y+height > size(A,1)-1, height = size(A,1)-y-1; end
