A VQ-Based Image Compression for Grey-Level Image Sequences 曾吉宏、陳永福
E-mail: [email protected]
ABSTRACT
A number of methods have been proposed for the compression of continuous image sequences. However, they only deal with binary images, which greatly limit their popularity in applications. In this thesis, we proposed a VQ-based method for compressing
continuous grey-level images which have great similarity between two adjacent images. Four sets of continuous image sequences, each consists of 9 images with image size of 256x256 pixels, were used for testing the performance of the proposed method. Each image was first segmented into a number of 3x3 or 4x4 blocks, and then LBG algorithm was used for training a set of codebook consisting of 512 codewords capable of delineating features of the continuous image sequence. For further increasing the
compression performance, JPEG-LS algorithm was applied to compress the codebook and index images of the sequential images.
The results show that the compression ratio achieved by using the proposed method is significantly higher than AVI, while the image quality of the reconstructed images has been hold at a satisfied level. Future works will expand the method to application of lossless compression in medical image sequences. Keywords - Vector quantization, continuous image, image compression, AVI.
Keywords : Vector quantization ; continuous image ; image compression ; AVI Table of Contents
目錄 封面內頁 簽名頁 授權書………iii 中文摘要………
………iv 英文摘要………v 誌謝………
………vi 目錄………vii 圖目錄………
………ix 表目錄………xi 方程式目錄…
………xii 第一章 前言………1 1.1 研 究動機………1 1.2 研究目的………2 1.3 論文架構………
………2 第二章 相關文獻介紹………3 2.1 無失真壓縮………
………3 2.1.1 JPEG-LS………4 2.1.2 JPEG2000………6 2.2 有失 真壓縮………9 2.2.1 向量量化(Vector Quantization)………9 2.2.2 MPEG………
………10 2.3 連續二元相似影像壓縮………11 2.4 AVI………
………13 第三章 研究方法………15 3.1 編碼簿訓練(codebook training)………
…………16 3.2 編碼與解碼(Encoding and Decoding)………18 3.3 以VQ為基礎的無失真連續灰階影像壓縮…………26 3.4 以PSNR為基礎尋找最適切割點………28 3.5 影像品質與效能評估………29 3.5.1 影像 品質評估………29 3.5.2 影像壓縮效能評估………31 第四章 實驗結果與討論…
………32 4.1 測試影像………32 4.2 重建影像之PSNR…………
………33 4.3 不同區塊大小對PSNR及壓縮比之影響…………38 4.4 編碼簿排序之影響………
……39 4.5 與AVI比較………41 4.6 無失真壓縮之比較………41 4.7 以PSNR為基礎尋找切割點之結果………42 第五章 結論………46 參考 文獻………..47 圖目錄 圖2.1 JPEG-LS方塊圖………
…………4 圖2.2 JPEG2000流程圖………6 圖2.3 有無做ROI之比較圖………
………8 圖2.4 GOP組成示意圖………10 圖2.5利用四分樹來表示二元影像………
………11 圖2.6四分樹範例………13 圖3.1 LBG演算法流程………
………16 圖3.2影像切割成數個小區塊………19 圖3.3初始編碼簿與編碼字…………
………19 圖3.4歐基里得距離之計算………20 圖3.5新重心之計算………
………20 圖3.6以全域搜尋找尋區塊x最近之編碼字………21 圖3.7編碼字之索引值取代區 塊x………21 圖3.8編碼與解碼流程………22 圖3.9排序前後之編碼簿
………23 圖3.10 MSB 影像與8 bits 影像………24 圖3.11以VQ為基礎 的有失真壓縮方法之過程………25 圖3.12以JPGE-LS做最後之壓縮………26 圖3.13取得符號 影像與差值影像………27 圖3.14取得符號影像與差值影像之範例………28 圖4.1四 組影像壓縮後的重建影像PSNR值之折線圖…………33 圖4.2 A組之連續9張原始灰階影像………34 圖4.3
A組之連續9張重建灰階影像………34 圖4.4 B組之連續9張原始灰階影像………35 圖4.5 B組之連續9張重建灰階影像………35 圖4.6 C組之連續9張原始灰階影像………
…36 圖4.7 C組之連續9張重建灰階影像………36 圖4.8 D組之連續9張原始灰階影像………
……37 圖4.9 D組之連續9張重建灰階影像………37 圖4.10不同區塊大小壓縮比之直條圖………
………39 圖4.11編碼簿排序前與排序後的CR值之直條圖………40 圖4.12無失真方法壓縮比之直條圖………
………42 圖4.13與第一張影像做PSNR比較之折線圖………43 圖4.14第一次切割剩餘影像與第22張影像 做PSNR比較之折線圖………44 圖4.15第二次切割剩餘影像與第43張 影像做PSNR比較之折線圖………44 圖4.16第21張與第22張之影像…
………44 圖4.17第42張與第43張之影像………45 圖4.18以PSNR為基礎之平 均PSNR值和壓縮比之直條圖……45 表目錄 表4.1四組影像壓縮後的重建影像之PSNR值………33 表4.2不同區塊 大小之平均PSNR與壓縮比………38 表4.3編碼簿排序前與排序後的CR值………40 表4.4 與AVI的CR值做比較.………41 表4.5比較與JPLEG-LS和JPEG2000-Lossless之壓縮比………42 表4.6以PSNR為基礎之平均PSNR值和壓縮比………45
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