Optimization Of Lossless Compression Algorithm For Solar Magnetic Field Image And Design Based On FPGA

With the development of astronomy;the research on spatial image is becoming more and more important.In order to exqlore the influence of solar magnetic field on space environment and celestial activities,the research on the background model of the Advanced Space-based Solar Observatory(ASO-S)has been approved by the Academy of Space Science of the Chinese Academy of Sciences.The aim is to develop a solar probe satellite used for imaging observation of solar magnetic field image.While high-quality images of solar magnetic field are being captured by satellites,a large amount of data is obtained.The return of such data is limited by transmission channels and storage resources.Therefore,it is necessary to compress the image of the solar magnetic field in orbit before transmission.The compression algorithms commonly used in the field of spatial image compression are not specific to this image.It is difficult to achieve high compression ratio under the premise of no data loss.In this thesis,the lossless compression algorithm for solar magnetic field image is explored.Through the analysis of image redundancy,the algorithm is studied in two aspects:preprocessing method and entropy coding method.Then,the algorithm is designed based on FPGA to improve the compression efficiency.The main work and achievements are as follows:(1)The(5,3)integer wavelet transform algorithm is studied based on MATLAB.After the application of this algorithm,the entropy of solar magnetic field image is reduced and the limit compression ratio is increased.This algorithm is selected as the main pretreatment method.(2)According to the pixel features of the solar magnetic field image,the RICE lossless compression algorithm is improved appropriately.The adaptive entropy coding part is taken as the entropy coding method of the algorithm studied in this thesis.(3)Combining(5,3)integer wavelet transform algorithm with improved RICE algorithm,the whole lossless compression algorithm is studied based on MATLAB.Two algorithms are proposed for a single solar magnetic field image.Then,the algorithm is forther optimized to make the compression ratio as high as 4.465,which is better than the existing algorithm.An algorithm is proposed for multiple images of solar magnetic field,and the compression ratio can be up to 5.668,meeting the engineering requirements.(4)The optimized bssless compression algorithm of solar magnetic field image is designed based on FPGA.The existing RICE algorithm is improved appropriately,and the preprocessing of(5,3)integer wavelet transform and data partitioning are designed.Then,the design is simulated and analyzed.The results are verified by bading the development board for debugging.Through simulation and verification,the design can mset the requirements of lossless compression of solar magnetic field image.And it meets the practical requirements in compression ratio and time.