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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/28250

Title: Variable Blocksize Wavelet Transform Image Coding
可變動區塊之小波轉換影像編碼
Authors: Jia-Chyi Wu;Ming-Kai Shi
吳家琪;施銘鎧
Contributors: NTOU:Department of Communications Navigation and Control Engineering
國立臺灣海洋大學:通訊與導航工程學系
Keywords: 四分樹分割;小波轉換;位元分配;向量量化
ouadtree segmentation;wavlet transform;bit allocation;vector quantization
Date: 2005
Issue Date: 2011-10-21T02:36:28Z
Publisher: Journal of Science and Engineering Technology
科學與工程技術期刊
Abstract: 摘要:小波轉換(wavelet transform)可提供具有對影像多重解析(multi-resolution)的功用,所以被廣泛地使用在影像壓縮技術上。而為了增加影像的壓縮比率,一般將小波轉換後的小波係數經由向量量化(vector quantization)來進行壓縮,而使用向量量化的主要原因是由於它具有很高的壓縮比率,而且在解壓縮時也相當容易。但在實用上,影像壓縮法除了壓縮比率外,編碼速度也是考量的重點。所以在本研究中,我們提出四分樹分割法作為影像的前處理(preprocessing),將影像的背景和細節部分分割成尺寸大小不同的區塊,然後將小波轉換後,在將每一個子頻帶區塊的小波係數能量(variance)作為位元分配的依據。而依照分配到的位元選擇最適當的編碼簿(codebook),並由編碼後所得的失真質來調整位元率。這樣的壓縮方式下,在低位元率時依然保有良好的視覺品質,而且由於編碼簿變得較小,所以運算速率也相對加快許多。本文所提方法的成果與效能及處理時間將於模擬結果處展示。
abstract:The wavelet-transform procedure has received considerable attention because it provides a multiresolution representation of images. By the way of a vector quantization technique,the wavelet transformed coefficients can be compressed further. For real-time image compression, achieving a high-data compression radio and coding efficiency simultaneously are both important. In this study,a quadtree segmentation method for image preprocessing is proposed. A quadtree segmentation algorithm is used to divide a given image, in which regions with image detail will be segmented into blocks with smaller sizes, and the background of he image will be assignd larger block sizes. After the wavelet transform, to select an appropriate size for the codebook,a bit assignment is applied to adjust the compressed bit rate. For this proposed compression scheme,the simulation results indicate that an acceptable visual quality and a high compression radio can achieved simultaneously. Furthermore, due to the small size of the code book, the computational time can be reduced. A system performance analysis is also demonstrated in this study.
Relation: 1(2), pp.57-67
URI: http://ntour.ntou.edu.tw/handle/987654321/28250
Appears in Collections:[通訊與導航工程學系] 期刊論文

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