利用區塊間冗餘資料提高JPEG 2000影像壓縮效能之研究

Abstract

近年來，隨著數位手機的普及，影像檔案也必須越小越好以達到更好的傳輸或儲存效率。在此應用環境之下，如何將影像的儲存空間做進一步的壓縮就成為一個日漸重要的課題。本研究所提出的方法利用區塊間的冗餘資料對影像做進一步的壓縮。實作上，在壓縮端以快速的方法判斷出適合被捨棄的區塊，而在解壓縮端利用影像區塊填補的技術，完整地補回被捨棄的區塊。藉此我們便可以達到進一步壓縮影像檔案的目的。實驗顯示，在低倍率的壓縮時我們的方法確實可以節省許多儲存空間，同時維持了良好的影像品質，而在高倍率的壓縮，我們的方法又能保持比純JPEG 2000更清析銳利的影像品質。

In recent year, with the mobile phone with integrated digital camera becoming more and more popular, the size of image file is required smaller to achieve better storage or transmission efficiency. In order to fit such kind of application environments, how to compress the image file to a smaller size has become a more and more important topic. The method proposed in this paper utilizes the inter-block redundancy to further compress an image by a fast algorithm to drop redundant blocks in the encoder side and to utilize our block filling method to fill them back in the decoder. In this way, we can achieve the goal of further compressing an image file. Experimental results indicate that in high compression ratio the proposed method can indeed improve the compression ratio and meanwhile maintain a proper visual quality and on the other hand in low compression ratio the method is capable to maintain a finer image quality compared to pure JPEG 2000 standard.