we proposed the algorithm by using the combination of sliding neighborhood block of MATLAB and Robert gradient operator.

The edge information of face region can be extracted with Robert operator after positioning the face area,then,detecting the circle with the geometry property of circle in the located eye area.

In order to get the thin gray edge that remains the information,the edge thinning algorithm is studied,and the edge thinning algorithm based on Robert operator is proposed.

Algorithm for Edge Detection Based on Fast Weighting Gradient Operator;

Finally,the whole continuous and close face contour is obtained by extracting upper face contour in the face region and by extracting chin contour through a gradient operator.

Meanwhile, the problem of solutions to second order system and a type of gradient operators equations in Hilbert space are studied by means of critical point theory.

Influence of gradient operators on inverse compositional gradient algorithm;

Hence four different gradient operators are used to compute the local orientation.

This paper introduces a new algorithm for a color image edge detection based on the classical algorithm ″sobel″ in HSV space,but two gradient algorithms(45 ° and 135 ° namely) are added in.

Principle and characteristic of P-M diffusion for image denoising are analyzed in theory,and the selection of parameter k of the P-M diffusion is analyzed also,the numerical calculation method of the gradient algorithm in the application of image denoising is discussed,and the improved P-M diffusion algorithm is obtained based on the method of traditional P-M diffusion.