Non-Linear Edge Enhancement

Non-linear edge enhancements are performed using non-linear combinations of pixels. Many algorithms are applied using either 2x2 or 3x3 kernels. 

The Sobel edge detector is based on the notion of the 3x3 window and is computed according to the relationship  

The operator detects horizontal, vertical, and diagonal edges. Each pixel in an image is declared an edge if its Sobel values exceeds some user-specified threshold. This information may be used to create the edge map, which often appears as a white line on a black background or vice versa. 

The gradient filters used to imply enhancement of edge gradient in two orthogonal directions, i.e., row and columns. In Kirsch the edge enhancement is carried out in 8 modulo. The gradient directions are East, North-east, North, North-west, West, South-west, South, and South-east. The template gradient 3x3 impulse response arrays were used where the scale factor was 1/15 [10], 

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The Kirsch non-linear edge enhancement calculates the gradient at pixel location BV . The algorithm applied is ... 

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