Inplace 2D matching in compressed images

The compressed matching problem, defined in [1] is the problem of finding a occurrences of a pattern in a compressed text. In this paper we discuss the 2-dimensional compressed matching problem in Lempel-Ziv compressed images. Given a pattern of (uncompressed) size m x m, and a text of (uncompressed) size n x n, both in 2D-LZ compressed form, our algorithm finds all occurrences of P in T. The algorithm is strongly inplace, that is, the amount of extra space used is proportional to the best possible compression of a pattern of size m 2. The best compression that the 2D-LZ technique can obtain for a file of size m(2) is O(m). The time for performing the search is O(m(2)) and the preprocessing time is O(m(3)). Our algorithm is general in the sense that it can be used for any 2D compression which can be sequentially decompressed in small space.