In this paper, a new image authentication scheme based on quadtree segmentation is presented. In this scheme, partial digital signature encryption is employed to ascertain the origin of the image. Furthermore, the quadtree structure is imposed on the design of the authentication code. The authentication code consists of the quadtree list and the mean values of the quadtree leaf nodes. The size ...

In this paper we introduce efficient parallel quadtree construction and manipulation algorithms on hypercube multiprocessors. The notion of extended binomial tree is introduced to represent the distributed quadtree structure on a hypercube. By incorporating the geometric property into the distributed quadtree structure, we devise a data assignment scheme which satisfies the multi-level adjacenc...

In this paper, the quadtree data structure and conforming polygonal interpolants are used to develop an h-adaptive finite element method. Quadtree is a hierarchical data structure that is computationally attractive for adaptive numerical simulations. Mesh generation and adaptive refinement of quadtree meshes is straight-forward. However, finite elements are non-conforming on quadtree meshes due...

The variable length code design of a complete quadtree-based video codec is addressed, in which we jointly optimize the entropy-coding for the parameters of motion-compensated prediction together with the residual coding. The quadtree coding scheme selected for this optimization allows easy access to the rate-distortion costs, thus making it possible to perform rate-distortion optimized bit all...

Spatial data representation and compression has become a focus issue in computer graphics and image processing applications. Quadtrees, as one of hierarchical data structures, basing on the principle of recursive decomposition of space, always offer a compact and efficient representation of an image. For a given image, the choice of quadtree root node plays an important role in its quadtree rep...

In this thesis we study two research aspects of geographical routing: efficient geographical addressing and a new routing scheme. In the first part we offer a novel geographical routing algorithm that relies on a well known data structure called Quadtree. Quadtree is an efficient method of mapping a twodimensional area by recursively partitioning it to disjoint squares. We present a greedy, gua...

We demonstrate that a resolution-r PR quadtree contaihing II points has, in the worst case, at most 8&r [log,(rt/2)]) + 8n/3 l/3 nodes. This captures the fact that as n tends towards 4’, the number of nodes in a PR quadtree quickly approaches O(n). This is a more precise estimation of the worst case space requirement of a PR quadtree then has been attempted before.

A modification of the linear quadtree [3], the threaded linear hierarchical quadtree (TLHQT), is proposed for the computation of geometric properties of binary images. Since most of the algorithms used in connection with computation of geometric properties require frequent exploration of adjacencies, a structure which keeps permanently in memory some adjacency links is introduced. In this paper...