TRLE-an efficient data compression scheme for image composition of volume rendering on distributed memory multicomputers

摘要

Data compression is a well-known method to improve the image composition time of parallel volume rendering on distributed memory multicomputers. In this paper, we propose an efficient data compression scheme, the template run-length encoding (TRLE) scheme, for image composition. Given an image with 2n x 2n pixels, in the TRLE scheme, the image is treated as n x n blocks and each block has 2 x 2 pixels. Since a pixel can be a blank or non-blank pixel, there 16 templates in a block. To compress an image, the TRLE scheme encodes an image block by block similar to the run-length encoding scheme. However, the TRLE scheme can filter out or use small space to encode blocks whose four pixels are blank pixels, that is, the TRLE scheme can encode a partial image according to the shape of non-blank pixels. To evaluate the performance of the TRLE scheme, we compare the proposed scheme with the BR, the RLE, and the BRLC schemes. Since a data compression scheme needs to cooperate with some data communication schemes, in the implementation, the binary-swap, the parallel-pipelined, and the rotate-tiling data communication schemes are used. By combining the four data compression schemes with the three data communication schemes, we have twelve image composition methods. These twelve methods are implemented on an IBM SP2 parallel machine. Four volume datasets are used as test samples. The data computation time and the data communication time are measured. The experimental results show that the TRLE data compression scheme with the rotate-tiling data communication scheme outperforms other eleven image composition methods for all test samples.