We take a threshold to compare with the gradient value of pixel P to decide the existence of an edge.
The Anisotropic Filtering method [32] convolves the image pixel in the direction orthogonal to the gradient of the pixel.
where,,, and is the local gradient of a pixel based on Sobel operator with masks and, respectively.
It is the summation of gradient of every pixel in the current CU by applying Sobel operator, which reveals the flatness of the CU.
The gradient of each pixel is calculated according to g ( x, y ) = S x 2 + S y 2 and a threshold value t is selected.
Step 1. Gradient computation: The gradient of each pixel in the window is calculated using two filter kernels: [−1, 0, 1] and [−1, 0, 1] T. Let the magnitude and orientation of the gradient of the i th pixel (1 ≤ i ≤ 4096) be denoted by m i and φ i, respectively.
The maximum absolute value of the eight convolutions is taken as the one representing the local gradient of the pixel's neighbourhood, and its corresponding direction should be considered when minimizing the Laplacian magnitude anisotropically.
Window size depends on the average gradient of the pixels in the area, as described as follow.
Secondly, in order to avoid long-term iteration in the manner of traditional anisotropic diffusion, the different speed of flow approach was introduced into the new technique as a selective smoothing switch according to effects by intensity and curvature gradient of neighbor pixels.
