![]() ![]() The importance of compression operation forces us to seek an effective method of data compression efficient method of data compression will be characterized by the following features. LZW Compression The GIF format uses LZW (Lempel-Zev-Welch) compression, which takes advantage of repetition in data streams. Image compression plays an important role in other areas, including tele-video conferencing, remote sensing, storage, and transmission of binary, gray scale, and color images. representing output code BA 256 B 66 AB 257 A 65 BAA 258 BA 256 ABA 259 AB 257 AA 260 A 65 AA 260 LZW Decompression The LZW decompressor creates the same string table during decompression. Thanks go to 'Wael AlGhool.' 15-01-2008: update the pseudo code of the compression. 1-1-2008: solved the bug of end file mismatch for big files compression. ![]() Compression operation is used to reduce the image size by a factor called compressing ratio (CR), which is equal the original image size divided by the compressed file size (see figure 4), and for effective method of compression this factor must be greater than 1, and the higher its value, the more effective the method of compression Compression reduces the transmission time by reducing the image size, for example: residential internet connections deliver data at speeds ranging 56 Kbps via conventional phone lines to more than 12 Mbps for broadband, the time required to transmit a small 128x128x24 bit full color image over this range of speeds is from 7 to 0.03 seconds, if CR=20, then range will be reduced to 0.35 to 0.0015 seconds. Download as PPT, PDF, TXT or read online from Scribd. 20-1-2005: I have solved a very special bug in the decompression, if any one took the code before this date, please update it.
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