**4. Stability Analysis of Multifractal Feature Descriptors**

The feature descriptors (*α*min, *α*max, *f*max) extracted from the multifractal spectrum should be able to characterize the significant textural information of the inertinite macerals. As is well known, effective texture features for image recognition are supposed to be robust and not subject to image quality. In this section, we consider the stability of our multifractal descriptors in terms of noise immunity and anti-blurring ability, and then illustrate the superiority of multifractal descriptors compared to the traditional feature descriptors.
