In this paper, we provide insight into the development of a new set of distortion-invariant texture operators. These `circular-Mellin' operators are invariant to both scale and orientation of the target and represent the spectral decomposition of the image scene in the log-polar coordinate system. Coupled with the shift invariance property of the correlator architecture, we show that these circular-Mellin operators can be used for rotation-, scale-, and shift- invariant feature extraction. We also note that these feature extractors have a functional form that is similar to the Gabor transforms. Detailed analytical description of these operators and preliminary results are presented in this paper.