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題 名 | Mixed-Transform Image Coding with Variable Block Sizes=區塊大小可彈性變化的混合式轉換影像編碼 |
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作 者 | 胡能忠; 張鴻義; | 書刊名 | 中國工程學刊 |
卷 期 | 22:4 1999.07[民88.07] |
頁 次 | 頁499-507 |
分類號 | 448.5 |
關鍵詞 | WHT轉換; DCT轉換; 影像編碼; 可變區塊大小; WHT; DCT; Image coding; Variable block; |
語 文 | 英文(English) |
中文摘要 | 在本論文中我們介紹了一種新的影像編碼技術,它同時採用了 Walsh-Hadmard Transform ( WHT )及 Discrete Cosine Transforem ( DCT )兩種轉換,並且能彈性決 定分割影像區塊的大小。首先待編碼影像以 16 × 16 的區塊大小加以割,每一分割好的影 像小塊先以 WHT 進行轉換,轉換後所得之係數有 16 個, 其中三個可用來決定該區塊是否 為複雜之影像區塊,若為複雜區塊則將 16 × 16 區塊細分為四個 8 × 8 區塊,並改以 8 × 8 DCT 加以編碼,若該區塊非複雜區塊則直接以 16 × 16 WHT 加以編碼。 針對非複雜 區塊而言 WHT 的編碼誤差近似於 DCT,但 WHT 的運算量卻遠小於 DCT,因此,這樣的編碼 架構能在不損及 PSNRs 的條件下節省大量的數學運算, 以我們實驗的九個影像編碼為例, 當壓縮率為 0.5bit/pixel 且保持相同 PSNRs 的條件下,本文提出之架構與僅使用 8 × 8 DCT 來進行編碼之傳統架構相較,本文提出之架構僅增加了 4.18% 的加法卻節省了 78.53% 的乘法。 |
英文摘要 | In the proposed image coding, variable block size and two transforms are used in image transform coding. A 16×16 image block is detected to be active or inactive according to activity indexes which are the values of three transform coefficients. If the image block is active, then it is partitioned to four 8×8 image blocks and then processed by a 2-D 8×8 discrete cosine transform (DCT); otherwise it is processed by a 2-D 16×16 Walsh-Hadmard transform (WHT) directly since the WHT has simple structure and the same image compression performance as the DCT does for inactive image blocks. As a result, the proposed approach is to process image blocks by a 16×16 WHT or an 8×8 DCT. If the PSNRs for both the conventional DCT image coding and the mixed-transform coding are kept the same in our experiments with 9 images, the number of additions of the latter increases by 4.18% on average, but the number of the multiplications decreases by 78.53% at bit rate 0.5. |
本系統中英文摘要資訊取自各篇刊載內容。