提升JPEG影像品質之技術

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Title:	提升JPEG影像品質之技術
Other Titles:	Image quality improvement for JPEG images
Authors:	蔡繼賢;Tsai, Chi-Shien
Contributors:	淡江大學資訊工程學系資訊網路與通訊碩士班林慧珍
Keywords:	影像壓縮;DCT轉換;量化;image compression;JPEG;DCT transformation;Quantization;PSNR
Date:	2013
Issue Date:	2014-01-23 14:38:27 (UTC+8)
Abstract:	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。 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..
Appears in Collections:	[Graduate Institute & Department of Computer Science and Information Engineering] Thesis

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