An example of rows and columns of the transform matrix H shown in Fig. 6 showing the different behaviour between Fredholm and convolution cases. The symmetry of the rows and columns of the convolution case is lost in the Fredholm case, as expected. Due to the lexicographic order for the image of 128 × 128 points, there is a pseudo periodicity of 128 elements of the matrices H (except for edge effects). Each row and column is made of 16384 points, which makes it difficult to draw.