is used to move the edge neighborhood closer to the edge, and
the areas between edges are stretched. The method has several
parameters, and the choice of optimal values for the best result
is not easy. Due to the global nature of the method the resulting
shapes of the edges are sometimes distorted.
In [9] the warping map is computed directly using the values
of left and right derivatives. In both methods [8] and [9] the pixel
shifts are proportional to the gradient values. It results in over-
sharpening of already sharp and high contrast edges and insuffi-
cient sharpening of blurry and low contrast edges. Both methods
also introduce small local changes in the direction of edges and
produce aliasing effect due to calculation of horizontal and ver-
tical warping components separately.