Pyramid Structure Using Projection for Progressive Image Transmission

Abstract

In this paper, we propose a progressive image transmission technique using hierarchical pyramid data structure which is constructed based on the projection data of an image. To construct the hierarchical Gaussian pyramid, we first divide an image into 4 × 4 nonoverlapping subblocks and generate the projection data of each subblock along the horizontal, vertical, diagonal, and antidiagonal directions. Among four images reconstructed by backprojecting the projection data along each direction, the image giving the minimum distortion is subsampled to construct the Gaussian image. The Gaussian pyramid is recursively generated by the proposed algorithm and the resulting Gaussian images preserve well-edge information. Based on the projection concept, a new encoding technique of the lowest Laplacian plane is also presented. Computer simulation with several test images shows that the quantitative performance of the proposed progressive image transmission technique using projection is similar to that of the conventional methods with its transmission bit rate reduced by 0.1-0.2 bit per pixel (bpp). Its subjective performance is also better because of the edge-preserving property of a projection operation.