應用於顯示器裝置之視覺無失真圖像壓縮法 ; Visually Lossless Image Compression Method for Display Devices

本論文針對顯示器裝置提出一個新穎的視覺無失真圖像壓縮技術。為了達到近乎無失真的圖像品質，採用較不易出現預測誤差的方向性預測器，以額外傳送預測模式來提高預測精準度。另外，演算法探討了人眼視覺系統（Human Visual System）中人眼對於不同圖像區域內錯誤感知的差異，根據區域內的複雜度將編碼單位分類為平滑、邊緣及無規則三種區域。在不同分類區塊使用不同的量化位階以達到視覺無失真及高壓縮率的目標。最後根據差值的機率分布，設計一改良式的一元編碼來進行更有效率的壓縮。另一方面，論文所提出的演算法架構只需使用兩條列記憶體，適用於行動裝置有限的線路面積，且低複雜度的計算更易於硬體實現。由實驗結果可得知，各類型的測試圖像以我們所提出的方法進行壓縮，在人眼無法察覺失真的壓縮品質下，皆可達到3倍以上的壓縮率。 ; This paper proposes a new visually lossless image compression technique for display devices The algorithm explores the differences in error perceptibility of human visual system (HVS) for different image areas Coding units are classified into smooth edge and random areas based on local complexity and prediction errors In order to achieve the objectives of imperceptible quality loss and high compression ratio the classified blocks are quantized by different levels The proposed architecture is designed to use only the memory of two line buffer so it is hardware-friendly and could be easily implemented in many display devices Experimental results show that the proposed method is visually lossless in all categories of tested images with the compression ratio 3