| The study content of this thesis is to design and implement a lossless compression algorithm for the full-surface solar magnetic field image,which is part of the project of the Advanced Space-based Solar Observatory(ASO-S)background model.Currently,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 and launch a solar observation satellite to study the relationship among the solar magnetic fields,solar flares and coronal mass ejections by shooting the full-surface solar magnetic field images.Since the transmission resources are limited,high quality astronomical image data return is a difficult problem.This study is aimed at lossless compression of high quality solar images before data transmission.Recently,the field of astronomical image compression is mostly compressed using JPEG2000 and wavelet transform algorithms,including lossy compression involving quantization,which is unfavorable to astronomical research.In addition,the compression method based on software is slow and inefficient,so it is better to implement lossless compression by hardware.Therefore,it is valuable to study the lossless compression algorithm for the full-surface solar magnetic field images and achieve it by hardware.The main work and achievements of the study in this thesis are divided into the following points.(1)The compression ratio of existing lossless compression method on the full-surface solar magnetic field images is studied.In the compression test of the images,the maximum compression ratio of several types of compression software on the images is 2.053.(2)On the MATLAB platform,the features of the images are analyzed,and the image preprocessing method is studied based on the Huffman lossless compression coding in the software.According to the study,the same channel subtraction preprocessing method between images and the pixel by pixel subtraction preprocessing method within one image are obtained.(3)Based on RICE algorithm,a lossless compression algorithm for the solar magnetic field image is programmed on the MATLAB platform.The improved special lossless compression algorithm has a better compression ratio for the images than most of the compression software,and the compression ratio of the single image can be up to 2.084.(4)The algorithm is implemented on the FPGA platform by means of Verilog language,and by optimizing the algorithm structure,the occupied area and power consumption are reduced.The algorithm passes the logical simulation and hardware verification,and the maximum working frequency can reach 40.15MHz.The study meets the design requirements of the current project. |
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