On the relation between Memon's and the modified Zeng's palette reordering methods

Palette reordering has been shown to be a very effective approach for improving the compression of color-indexed images by general purpose continuous-tone image coding techniques. In this paper, we provide a comparison, both theoretical and experimental, of two of these methods: the pairwise merging heuristic proposed by Memon et al. and the recently proposed modification of Zeng's method. This analysis shows how several parts of the algorithms relate and how their performance is affected by some modifications. Moreover, we show that Memon's method can be viewed as an extension of the modified version of Zeng's technique and, therefore, that the modified Zeng's method can be obtained through some simplifications of Memon's method.