Gray level size zone matrix


The gray level size zone matrix is the starting point of Thibault matrices. It is an advanced statistical matrix used for texture characterization.
For a texture image f with N gray levels, it is denoted and provides a statistical representation by the estimation of a bivariate conditional probability density function of the image distribution values. It is calculated according to the pioneering run length matrix principle : the value of the matrix is equal to the number of zones of size and of gray level. The resulting matrix has a fixed number of lines equal to N, the number of gray levels, and a dynamic number of columns, determined by the size of the largest zone as well as the size quantization.
The more homogeneous the texture, the wider and flatter the matrix. SZM does not required computation in several directions, contrary to RLM and co-occurrence matrix. However, it has been empirically proved that the degree of gray level quantization still has an important impact on the texture classification performance. For a general application it is usually required to test several gray-level quantization to find the optimal one with respect to a training dataset.

Examples

Two examples of matrix filling for textures 4 × 4 with four gray levels.