The Design Of PNG Decoder Hardware Accelerator

PNG(Portable Network Graphics) is a lossless picture format with public algorithm.It encodes data with hign compression ratio, which makes the compressed data easy tobe transferred and keeps the quality of the original image. It supports the transparentcolor. Because it has so many advantages, PNG has been widely used on the webpageand OSD.This paper makes an elaborate study of PNG image, and introduces the ASICdesign of the PNG decoder. Firstly, we explain the data element and the data format,illustrate the main steps of PNG Encoder. Through these studies, we formed a quitecomplete basic knowledge of PNG image and lay a theoretical foundation for the furtherstudy for the PNG Decoder. Secondly, we did a research on the principle of the twocompressed algorithms used in PNG Decoder and an explaination on the modificationin the PNG spec when the two compressed algorithms are used at the same time. Iproposed several feasible hardware structures for each algorithm. Then, according to thestudy of the decoding process, we introduced the hardware design and verification ofthe PNG Decoder. We divided the whole decoder into several modules and gave thedetails of the main modules. Finally, according to the problems in the research, Ipropose the improvement measures and future research.Only software verification is finished to this design. Testcases are the images in thePngSuite the PNG official website provides which incudes several images special fortesting our design. Result shows that the design can decode the images correctly.