% Created by Majed El Helou (2017)
% All rights reserved for EPFL.

function [ I1mask, I2mask, patch_corr ] = corrAcrossPatches(I1,I2,patch_size,peroverlap)
%corr_across_patches returns a map that shows the correlation between
%patches of size patch_size in I1 and I2, with % overlap = peroverlap
%if image size is not a multiple of patch_size, the remainder is ignored
%if images have different sizes, the correlation is over their intersection

ximage_size = min( size(I1,1), size(I2,1) );
yimage_size = min( size(I1,2), size(I2,2) );

xpatches_total = floor( ximage_size/patch_size );
ypatches_total = floor( yimage_size/patch_size );

patch_corr = zeros(xpatches_total, ypatches_total);

if peroverlap == 0
    for pix = 1:xpatches_total
        xi_image = (pix-1)*patch_size + 1;
        xf_image = xi_image + patch_size - 1;
        for piy = 1:ypatches_total
            yi_image = (piy-1)*patch_size + 1;
            yf_image = yi_image + patch_size - 1;
            patch_corr(pix,piy) = corr2( I1(xi_image:xf_image,yi_image:yf_image)...
                , I2(xi_image:xf_image,yi_image:yf_image) );
            I1mask(xi_image:xf_image,yi_image:yf_image) = I1(xi_image:xf_image,yi_image:yf_image) > mean2(I1(xi_image:xf_image,yi_image:yf_image));
            I2mask(xi_image:xf_image,yi_image:yf_image) = I2(xi_image:xf_image,yi_image:yf_image) > mean2(I2(xi_image:xf_image,yi_image:yf_image));
        end
    end
else
I1mask=0;
I2mask=0;
    pixoverlap = floor( patch_size * peroverlap / 100 );
    % Initialize
    pix = 0;
    xf_image = pixoverlap;
    while true
        pix = pix + 1;          % x index counter
        xi_image = xf_image + 1 - pixoverlap;
        xf_image = xi_image + patch_size - 1;

        if xf_image > ximage_size
            break;
        end

        % Initialize
        piy = 0;
        yf_image = pixoverlap;
        while true
        	piy = piy + 1;      % y index counter   
            yi_image = yf_image + 1 - pixoverlap;
            yf_image = yi_image + patch_size - 1;

            if yf_image > yimage_size
                break;
            end
            patch_corr(pix,piy) = corr2( I1(xi_image:xf_image,yi_image:yf_image)...
                , I2(xi_image:xf_image,yi_image:yf_image) );

        end
    end
end