Daniel Moreno (damoreno)

The effect of texture flattening can be achieved by solving the Poisson equation using the gradients of the original image passed through a sieve function M. First, the edges are detected in the original image using the magnitude of the intensity gradient. I have used the Sobel operator to compute the intensity gradients. Then, the gradient magnitude image is thresholded to make a binary mask. The magnitude image is also used as a gradient sieve M that preserves the original image gradients at the edges and sets them to zero in the rest of the image. Finally, the same equations as before are solved to recompute the intensities in the flattened regions. Observe in the result column below how the image content is preserved but the small details were removed in the regions without edges.

Here we want to set to grayscale the original image except in the region covered by the mask. If we do it in the naive way, the final image will have a noticeable seam surrounding the mask. By using a procedure similar as for image cloning, the seam caused by the sudden change from color to grayscale is concealed.