【正文】 能力跟人類的需求有相當(dāng)大的差距。 隨著信息技術(shù)的發(fā)展，對(duì)靜止圖像和視頻序列圖像的壓縮編碼技術(shù)的應(yīng)用越來越廣泛，從家庭娛樂到專業(yè)的通信設(shè)備、從廉價(jià)的消費(fèi)電子產(chǎn)品到昂貴的專業(yè)級(jí)專用設(shè)備，應(yīng)用的例子舉不勝舉，如 VCD、 DVD、可視電話、視頻會(huì)議、 IP 上的視頻服務(wù)、數(shù)字圖書館、數(shù)字電視、高清晰電視、數(shù)碼照相機(jī)、數(shù)字圖像監(jiān)控等因此工業(yè)界對(duì)圖像壓縮專業(yè)人員的需求在不斷地增長。為了便于信息交換和方便使用，數(shù)字圖像必須以一定的格式存儲(chǔ)，如常用的 BMP、 JPEG、 GIF 等圖像文件格式。 MATLAB。 關(guān)鍵詞： JPEG；離散余弦變換； MATLAB；圖形用戶界面 Abstract II ABSTRACT The JPEG basic system coding based on MATLAB is introduced in this paper. The JPEG format is usually used to press static image during the process of image transmission. The JPEG basic system coding divides the gray image into several subimages of size 88 firstly. Discrete cosine transform is used to get the transform coefficient of subimage and then the transform coefficient is quantized. Secondly, Z type scan is adopted to get direct current (DC) coefficient and alternate current (AC) coefficient of the quantized transform coefficient. Thirdly, predictive coding and variablelength coding is used for DC and AC coefficient respectively. Finally, bit sequences of the pressed image are outputted by using entropy coding according to standard Huffman coding. Then image pression is realized. The user gets the reconstructed image by Huffman decoding, variablelength decoding of DC and AC coefficient, dequantization and reverse discrete cosine transform sequentially. MATLAB results of simulation demonstrate that there is no difference between reconstructed image and original image and reconstructed image can satisfy human visual requirements. Additionally, pression ratio is about 10 and peak signaltonoise ratio is all over than 30dB. Therefore, the realization of JPEG basic system coding using MATLAB is of s uch advantages as simple method, fast speed, small error and it can enhance the efficiency and accuracy of image pression greatly. Key words: JPEG。另外，數(shù)據(jù)壓縮比在 10 倍左右且峰值信噪比均在 30dB 以上。在接收端，經(jīng)過 Huffman解碼、直流系數(shù)和交流系數(shù)可變長解碼以及反量 化后，再進(jìn)行離散余弦逆變換后得到重建圖像。接著，對(duì)直流系數(shù)采用預(yù)測編碼，對(duì)交流系數(shù)采用可變長編碼。 JPEG 基本系統(tǒng)編碼首先把灰度圖像分成 88 的像素塊，然后對(duì)各個(gè)像素塊進(jìn)行離散余弦變換得到變換系數(shù)后再進(jìn)行量化。摘要 I 摘 要 本文介紹了基于 MATLAB 的 JPEG 基本系統(tǒng)編碼。在圖像傳送過程中，經(jīng)常采用 JPEG格式對(duì)靜止圖像進(jìn)行壓縮編碼。其次，對(duì)量化后的變換系數(shù)采用 Z形掃描，得到直流系數(shù)和交流系數(shù)。最后，根據(jù)標(biāo)準(zhǔn)的 Huffman編碼進(jìn)行熵編碼，輸出壓縮圖像的比特序列，從而實(shí)現(xiàn)圖像壓縮。 MATLAB 仿真結(jié)果表明：重建圖像與原始圖像幾乎沒有任何差異，能夠滿足人們的視覺需求。因此，采用 MATLAB實(shí)現(xiàn) JPEG 基本系統(tǒng)編碼具有方法簡單、速度快、誤差小等優(yōu)點(diǎn)，能夠大大提高圖像壓縮的效率和精度。 discrete cosine transform。 graphical user interface 目錄 i 目 錄 第 1 章 緒 論 ...................................................................................................... 1 圖像變換編碼概述及目前狀況 ........................................................................................... 1 論文結(jié)構(gòu) ............................................................................................................................... 2 第 2 章 MATLAB 簡介 ......................................................................................... 3 MATLAB 的發(fā)展簡史 .......................................................................................................... 3 MATLAB 的特點(diǎn) .................................................................................................................. 3 MATLAB 的功能 ................................................................................................................ 3 MATLAB 的技術(shù)特點(diǎn) ......................................................................................................... 4 MATLAB 圖像類型 .............................................................................................................. 5 GUI......................................................................................................................................... 5 第 3 章 變換編碼 .................................................................................................. 7 變換編碼的一般形式與意義 ............................................................................................... 7 基本原理 ............................................................................................................................... 7 正交變換的去相關(guān)性 .......................................................................................................... 8 變換編碼性能判斷 ............................................................................................................. 9 變換編碼的特點(diǎn) ................................................................................................................11 最佳正交變換 ——KL變換 ............................................................................................. 11 第 4 章 JPEG 圖像壓縮 ...................................................................................... 13 JPEG 概述 ............................................................................................................................ 13 JPEG 圖像編碼算法的 實(shí)現(xiàn) ................................................................................................ 14 離散余弦編碼 ................................................................................................................... 14 量化 ................................................................................................................................ 15 編碼 ................................................................................................................................. 16 JPEG圖像數(shù)據(jù)壓縮發(fā)展 ................................................................................................... 19 第 5 章 MATLAB 仿真 ....................................................................................... 21 系統(tǒng)模塊圖 ......................................................................................................................... 21 JPEG 壓縮編碼的設(shè)計(jì)流程 ................................................................................................ 21 目錄 ii 掃描順序變換 ............................................................................................................