imcrop.m

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function varargout = imcrop(varargin)
%IMCROP Crop image.
%   IMCROP crops an image to a specified rectangle. In the
%   syntaxes below, IMCROP displays the input image and waits for
%   you to specify the crop rectangle with the mouse:
%
%        I2 = IMCROP(I)
%        X2 = IMCROP(X,MAP)
%        RGB2 = IMCROP(RGB)
%
%   If you omit the input arguments, IMCROP operates on the image
%   in the current axes.
%
%   To specify the rectangle:
%
%   - For a single-button mouse, press the mouse button and drag
%     to define the crop rectangle. Finish by releasing the mouse
%     button.
%
%   - For a 2- or 3-button mouse, press the left mouse button and
%     drag to define the crop rectangle. Finish by releasing the
%     mouse button.
%
%   If you hold down the SHIFT key while dragging, or if you
%   press the right mouse button on a 2- or 3-button mouse,
%   IMCROP constrains the bounding rectangle to be a square.
%
%   When you release the mouse button, IMCROP returns the cropped
%   image in the supplied output argument. If you do not supply
%   an output argument, IMCROP displays the output image in a new
%   figure.
%
%   You can also specify the cropping rectangle noninteractively,
%   using these syntaxes:
%
%        I2 = IMCROP(I,RECT)
%        X2 = IMCROP(X,MAP,RECT)
%        RGB2 = IMCROP(RGB,RECT)
%
%   RECT is a 4-element vector with the form [XMIN YMIN WIDTH
%   HEIGHT]; these values are specified in spatial coordinates.
%
%   To specify a nondefault spatial coordinate system for the
%   input image, precede the other input arguments with two
%   2-element vectors specifying the XData and YData:
%
%        [...] = IMCROP(X,Y,...)
%
%   If you supply additional output arguments, IMCROP returns
%   information about the selected rectangle and the coordinate
%   system of the input image:
%
%        [A,RECT] = IMCROP(...)
%        [X,Y,A,RECT] = IMCROP(...)
%
%   A is the output image. X and Y are the XData and YData of the
%   input image.
%
%   Remarks
%   -------
%   Because RECT is specified in terms of spatial coordinates,
%   the WIDTH and HEIGHT of RECT do not always correspond exactly
%   with the size of the output image. For example, suppose RECT
%   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.
%
%   Class Support
%   -------------
%   The input image A can be of class uint8 or double. The output
%   image B is of the same class as A. RECT is always of class
%   double.
%
%   Example
%   -------
%        I = imread('ic.tif');
%        I2 = imcrop(I,[60 40 100 90]);
%        imshow(I), figure, imshow(I2)
%
%   See also ZOOM.

%   Clay M. Thompson 1-22-93
%   Copyright 1993-1998 The MathWorks, Inc.  All Rights Reserved.
%   $Revision: 5.9 $  $Date: 1997/11/24 15:35:22 $

[x,y,a,cm,rect,msg] = ParseInputs(varargin{:});
if (~isempty(msg))
    error(msg);
end

[m,n,o] = size(a);
xmin = min(x(:)); ymin = min(y(:));
xmax = max(x(:)); ymax = max(y(:));
% Transform rectangle into row and column indices.
if (m == 1)
    pixelsPerVerticalUnit = 1;
else
    pixelsPerVerticalUnit = (m - 1) / (ymax - ymin);
end
if (n == 1)
    pixelsPerHorizUnit = 1;
else
    pixelsPerHorizUnit = (n - 1) / (xmax - xmin);
end
pixelHeight = rect(4) * pixelsPerVerticalUnit;
pixelWidth = rect(3) * pixelsPerHorizUnit;
r1 = (rect(2) - ymin) * pixelsPerVerticalUnit + 1;
c1 = (rect(1) - xmin) * pixelsPerHorizUnit + 1;
r2 = round(r1 + pixelHeight);
c2 = round(c1 + pixelWidth);
r1 = round(r1);
c1 = round(c1);
% Check for selected rectangle completely outside the image
if ((r1 > m) | (r2 < 1) | (c1 > n) | (c2 < 1))
    b = [];
else
    r1 = max(r1, 1);
    r2 = min(r2, m);
    c1 = max(c1, 1);
    c2 = min(c2, n);
    b = a(r1:r2, c1:c2, :);
end

switch nargout 
case 0
    if (isempty(b))
        warning('The crop rectangle does not intersect the image');
    end
    figure;
    if (~isempty(cm))
        imshow(b,cm)
    else
        imshow(b);
    end
    
case 1
    varargout{1} = b;
    
case 2
    varargout{1} = b;
    varargout{2} = rect;
    
case 4
    varargout{1} = x;
    varargout{2} = y;
    varargout{3} = b;
    varargout{4} = rect;

otherwise
    error('Too many output arguments');
end

%%%
%%% Subfunction ParseInputs
%%%
function [x,y,a,cm,rect,msg] = ParseInputs(varargin)

x = [];
y = [];
a = [];
flag = 0;
cm = [];
rect = [];
msg = '';

switch nargin
case 0
    % IMCROP
    % Get information from current figure
    [x,y,a,flag] = getimage;
    if (flag == 0)
        msg = 'No image found in the current axes';
        return;
    end
    if (flag == 1)
        % input image is indexed; get its colormap;
        cm = colormap;
    end
    rect = getrect(gcf);
    
case 1
    % IMCROP(I) or IMCROP(RGB)
    a = varargin{1};
    x = [1 size(a,2)];
    y = [1 size(a,1)];
    imshow(a);
    rect = getrect(gcf);
    
case 2
    % IMCROP(X,MAP) or IMCROP(I,RECT) or IMCROP(RGB,RECT)
    a = varargin{1};
    x = [1 size(a,2)];
    y = [1 size(a,1)];
    if (size(varargin{2},2) == 3)
        % IMCROP(X,MAP)
        cm = varargin{2};
        imshow(a,cm);
        rect = getrect(gcf);
    else
        rect = varargin{2};
    end
    
case 3
    % IMCROP(x,y,RGB) or IMCROP(X,MAP,RECT)
    if (size(varargin{3},3) == 3)
        % IMCROP(x,y,RGB)
        x = varargin{1};
        y = varargin{2};
        a = varargin{3};
        imshow(x,y,a);
        rect = getrect(gcf);
    else
        % IMCROP(X,MAP,RECT)
        a = varargin{1};
        cm = varargin{2};
        rect = varargin{3};
        x = [1 size(a,2)];
        y = [1 size(a,1)];
    end
    
case 4
    % IMCROP(x,y,I,RECT) or IMCROP(x,y,RGB,RECT)
    x = varargin{1};
    y = varargin{2};
    a = varargin{3};
    rect = varargin{4};
    
case 5
    % IMCROP(x,y,X,MAP,RECT)
    x = varargin{1};
    y = varargin{2};
    a = varargin{3};
    cm = varargin{4};
    rect = varargin{5};
    
otherwise
    msg = 'Too many input arguments';
    return;
    
end