PSNR of two images of different size in matlab
When interpolating, why not use the same size as the image to compare with:

% some random inputs
original = rand(435,782);
img = rand(100,200);
% position where to interpolate
[x,y] = meshgrid(linspace(1,size(img,2),size(original,2)),linspace(1,size(img,1),size(original,1)));
% interpolate
dest = interp2(img,x,y,'bicubic');
% display size of result
disp(size(dest));