Similarity Retrieval by 2D C-Trees Matching in Image Databases

The image retrieval based on spatial content is an attracting task in many image database applications. The 2D strings provide a natural way of constructing spatial indexing for images and support effective picture query. Nevertheless, the 2D string is deficient in describing the spatial knowledge of nonzero sized objects with overlapping. In this paper, we use an ordered labeled tree, a 2D C-tree, to be the spatial representation for images and propose the tree-matching algorithm for similarity retrieval. The distance between 2D C-trees is used to measure the similarity of images. The proposed tree comparison algorithm is also modified to compute the partial tree distance for subpicture query. Experimental results for verifying the effectiveness of similarity retrieval by 2D C-trees matching are presented.