The Research And Implementation Of Image Encoding Based On FPGA

With the application of multimedia,large storage space is needed by image data,so image compression technology is widely used. With good compression performance, JPEG still image commpression standard has been widely applied in the image proce-ssing field.At the same time,with the maturity of integrated circuit technology,FPGA with its flexibility and large resources can be applied to image compression application, so it is of practical significance to use FPGA to achieve image encoding.Research work focuses on JPEG standard coding system based on FPGA and the mainwork of paper includes four parts:1) Ranks of the decomposition method is used to implement the two-dimensional discrete cosine transform. Due to the separability of the discrete cosine, two-dimen-sional discrete cosine transform can be achieved by twice one-dimensional discrete cosine transforms,so that the computation time is reduced. Distributed Algorithm is applied to implement one-dimensional discrete cosine transforms,so that the part of the processing efficiency is improved.2) Multiplication instead of division is applied to implement quantification. In order to reduce the impact of the division operation, reciprocal of quantization table is calculated firstly, then use multiplication to replace the division operation.3) Pass shift assignment is used to implement Z glyph scanning. Look-up table method is choosen to achieve Entropy coding. Z-word scan module is integrated in the entropy coding module.DC and AC coefficient are separately operated by Entropy coding module,and then choose look-up table method to achieve encoding.4) The color conversion module is implemented and write test code to verify its correctness.In the ISE development platform,a variety of modules are achieved by Verilog hardware description language and write respectively the test code to verify the correctness of the image coding.Validation is mainly through the Modelsim simulation. Modelsim waveform simulation results which belong to process of encoding were compared with MATLAB simulation results.After that data stream that is from FPGA encoding is saved to a file.At last encoding correctness is verified by the methods that the file is decoded and showed by image by MATLAB.