关键词: 纹理分析, 灰度共生矩阵, 旋转不变, 灰度-梯度共生矩阵

Abstract: In the process of the texture image recognition and classification，many images which have the same texture features usually show the diversity of direction.These images are supposed to be the same category.So the method how to get the rotation invariant features is needed.There are many methods to solve it，such as geometric moments，orthogonal moments，gray level co-occurrence etc.But the first two methods are time consuming，and the performance of the third is not satisfying.A method based on Gray-Gradient Co-occurrence Matrix is recommended to get the rotation invariant features.Furthermore，a fast algorithm for computing the Gray-Gradient Co-occurrence Matrix is proposed.Experimental results demonstrate that the method is very efficient for getting the rotation invariant features，and the fast algorithm has largely reduced the computation.

Key words: texture analysis, gray level co-occurrence matrix, rotation invariance, gray-gradient co-occurrence matrix