////////////////////////////////////////////////////////////////////
// Function COLOR_POISSON 
// Take two color images u and v and a binary mask. The image //v is assumed to be smaller than u. First a subimage of u 
// with the size of v is extracted at (x,y). Then, we copy the // part of v corresponding to the mask to this subimage of u, // and then u is reformed. 
// Author : Julie Delon, 2015. 
////////////////////////////////////////////////////////////////////

// Input parameters 
// - image u (large image)
// - image v (small image with portion to be copied in u)
// - mask (binary mask)
// - (x,y) integers, position in u where a portion of v must 
// be copied

// Output :
// - image out containing u and a portion of v cloned by 
// Poisson Editing

function out = color_poisson(u, v, mask, x, y, niter)
 [nr,nc] = size(v(:,:,1));
 ucrop = u(x:x+nr-1,y:y+nc-1,:); 

 for i = 1:3
 tmp(:,:,i) = poisson(ucrop(:,:,i),v(:,:,i),mask,niter);
 end

 out = u;
 out(x:x+nr-1,y:y+nc-1,:) = tmp;
 out = max(min(out,255),0);

endfunction

// Poisson editing for gray level images
function out = poisson(u, v, mask, niter)

 f = u.*(1-mask) + v.*mask;
 K=[0,1,0;1,0,1;0,1,0];
 lapv = laplacien(v);
 
 for k = 1:niter
 Kf = conv2(f,K,'same');
 f(mask) = 1/4*(Kf(mask) + lapv(mask));
 end

 out = f;
endfunction

// Compute the laplacian of an image u
function lap = laplacien(u)

 [ud,ub,ug,uh] = imdiff(u);
 lap = ud + ub + ug + uh;

endfunction


function [ud,ub,ug,uh] = imdiff(u)

 Kd = [ 0,1, -1 ];
 Kb = [ 0;1; -1 ];
 Kg = [ -1,1, 0 ];
 Kh = [ -1;1; 0 ];

 ud = conv2(u,Kd,'same');
 ub = conv2(u,Kb,'same');
 ug = conv2(u,Kg,'same');
 uh = conv2(u,Kh,'same');

endfunction