提升JPEG影像品質之技術

Image Quality Improvement for JPEG Images

蔡繼賢(Chi-Shien Tsai)

指導教授 ： 林慧珍

淡江大學/工學院/資訊工程學系資訊網路與通訊碩士班/碩士(2013年)

https://doi.org/10.6846/TKU.2013.01157

摘要

本論文提出一種改善JPEG解壓縮影像品質方法，為Chang et al. 所提方法之改進版本。在JPEG壓縮影像時，利用一個改進係數調整區塊(Modified Coefficient Adjustment Block)記錄各區塊之DCT係數在量化步驟因四捨五入所造成誤差的情形，當影像解壓縮反量化DCT係數時，再依照紀錄的情形來調整重建的DCT係數，進而轉換成解壓縮影像，由於各影像屬性不同(即量化步驟中被四捨五入之小數值分佈不同)，因此本論文提供兩種參數選擇方式來調整係數，及固定與自適性調整參數。
實驗結果顯示，固定與自適性參數調整皆比Chang et al. 所提的方法有明顯的改進。

關鍵字

影像壓縮 ； JPEG ； DCT轉換 ； 量化 ； PSNR

並列摘要

In this paper we proposed a method to enhance the quality of the decompressed JPEG images, which is an improved version of the method proposed by Chang et.al.. A so-called Modified Coefficient Adjustment Block is used to record the round off situation while DCT coefficients in a block are quantized according to a given quantization block. In the decompression stage, the information recorded in the Modified Coefficient Adjustment Block is then referred to adjust the de-quantized DCT coefficients before the Inverse DCT transformation. We provide two choices of parameter setting, fixed and adaptive parameters. Experimental results show that no matter whether fixed or adaptive parameters are used, our method provides significantly better results than The method proposed by Chang et al..

並列關鍵字

Image Compression ； JPEG ； DCT transformation ； Quantization ； PSNR

參考文獻

[1] D. Yu, F. Sattar and B. Barkat, “Multiresolution Fragile Watermarking using Complex Chirp Signals for Content Authentication,” Pattern Recognition, May 2006, Vol. 39, Issue 5, pp. 935-952.

[2] J. L. Liu, D. C. Lou, M. C. Chang, and H. K. Tso, “A Robust Watermarking Scheme using Self-Reference Image,” Computer Standards & Interfaces, Jan. 2006, Vol. 28, Issue 3, pp. 356-367.

[3] J. Fridrich, M. Goljan, and R. Du, “Detecting LSB Steganography in Color, and Gray-scale Images,” IEEE Multimedia, 2001, Vol. 8, No. 4, pp. 22-28.

[4] C. C. Chang, and H. W. Tseng, “A Steganographic Method for Digital images using Side Match,” Pattern Recognition Letters, Sep. 2004, Vol. 25, No.12, pp. 1431–1437.

[5] D. C. Wu, and W. H. Tsai, “A Steganographic Method for Images by Pixel-Value Differencing,” Pattern Recognition Letters, Jun. 2003, Vol. 27, No. 9-10, pp. 1613–1626.