The next step in the enhancement process is to construct the final filtered
image using the pixel values from the prefiltered images. This requires the value
of the ridge orientation at each pixel in the raw image and the filtering direction
of each prefiltered image. Each point in the final image is then computed by
selecting, from the prefiltered images the pixel value whose filtering direction
most closely matches the actual ridge orientation. The output of the filtering
stage is an enhanced version of the image that has been smoothed in the direction
of the ridges.