An Improved Similarity Measure for Image Database Based on 2D C+-string

Abstract

In an image database system, the spatial knowledge representation is a technique of abstraction to describe an image. The 2D string and its variants are based on this concept. One of the variants, called 2D C+-string, considers sizes of and distances between objects. This method presents three advantages: (1) more accuracy in picture rep- resentation and reconstruction; (2) less ambiguity in similarity retrieval; (3) reasoning about relative ocations for a symbolic picture is possible. How- ever, the similarity measure based on 2D C+-string doesn't consider the ratios about sizes of and dis- tances between objects on x- and y-axis together. This neglect may cause distorted result of similarity retrieval. In this paper, we modify the original sim- ilarity measure for taking down the variation of ra- tios between two symbolic pictures and furthermore propose two new types of similarity measure for dis- criminating pictures more precise. By exploiting the ratios, the pictorial query is more °exible for certain demands.