gridsplit.m

function im_array=gridsplit(im,grid_x,grid_y,width_fact,height_fact,left_extra,right_extra,top_extra,bottom_extra)
%Crops a grid of images out of one image
%   im_array=gridsplit(im,...) returns an image array im_array that has
%   size (MxNxPxR) in which M the width, N the height, P the channel and R
%   the amount of images destilled from the grid. So it puts all the 
%   gridparts in R which has size (grid_x*grid_y)
%   You get the idea. Otherwise more info on: www.timzaman.nl
%  
%   grid_x       = Amount of horizontal patches
%   grid_y       = Amount of vertical patches
%   width_fact   = You can define a horiz. border for each grid here
%                  (1=no border 0=nothing)
%   height_fact  = You can define a vertical border for each grid here
%                  (1=no border 0=nothing)
%   left_extra   = The left border it should exclude from the orig. image
%   right_extra  = The right border it should exclude from the orig. image
%   top_extra    = The top border it should exclude from the orig. image
%   bottom_extra = The bottom border it should exclude from the orig. image
%
%   Examples
%   --------
%   Gets a 4x6 grid from an image
%
%       I = imread('test.jpg');
%       im_array=gridsplit(im,6,4,0.5,0.5,10,10,10,10);
%       figure, imshow(I), figure, imshow(im_array(:,:,:,1))
%
%   Note
%   ----
%   This is the first version without much support
%
%   Class Support
%   -------------
%   The input image; bitonal, grayscale, or rgb; and should be 8bit of 16bit unsigned
%  
%   See also makecform, applycform
%   Written by Tim Zaman, TU Delft, 2011
%   This work, unless otherwise expressly stated, is licensed under a
%   Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
%   
%   THIS SOFTWARE IS PROVIDED BY TIM ZAMAN ''AS IS'' AND ANY
%   EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
%   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
%   DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> BE LIABLE FOR ANY
%   DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
%   (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
%   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
%   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
%   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
%   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
%
%
 
sz=size(im);
 
%Reduce width for grid-division later
sz(1)=sz(1)-(top_extra+bottom_extra);
sz(2)=sz(2)-(left_extra+right_extra);
 
%Calculate gridsizes and widths for later
gridsize=round([sz(1)/grid_y sz(2)/grid_x]);
gridsize_real=round([height_fact width_fact].*gridsize);
gridskip_left=round(((1-[height_fact width_fact])/2).*gridsize);
 
%Calculate start and end positions [x]
x_start=round(([0:grid_x-1]*(sz(2)/grid_x))+1+left_extra);
x_start=x_start+gridskip_left(2);
x_end=x_start+gridsize_real(2);
 
%Calculate start and end positions [y]
y_start=round(([0:grid_y-1]*(sz(1)/grid_y))+1+right_extra);
y_start=y_start+gridskip_left(1);
y_end=y_start+gridsize_real(1);
 
%Preallocation for speed
i=0; 
if strcmp(class(im),'uint16')==1
    im_array=uint16(zeros(gridsize_real(1)+1,gridsize_real(2)+1,sz(3),grid_x*grid_y));
else
    im_array=uint8(zeros(gridsize_real(1)+1,gridsize_real(2)+1,sz(3),grid_x*grid_y));
end
 
%Fills the array
for y=1:grid_y
    for x=1:grid_x
        i=i+1;
        im_array(:,:,:,i)=im(y_start(y):y_end(y),x_start(x):x_end(x),:);
    end
end