Quantization method of function graycomatrix

Hi everyone,

I would like to know which quantization method uses the function graycomatrix to establish the number of gray levels.

In the documentation page of the function, the parameter 'NumLevels' is defined as:

Number of gray levels, specified as an integer. For example, if NumLevels is 8, graycomatrix scales the values in I so they are integers between 1 and 8. The number of gray-levels determines the size of the gray-level co-occurrence matrix (glcm).

However, which method uses the function to scale the values?

Thank you in advance,

Rafa