lzw

Decode data bytes of GIF87a raster data stream

由 穿精又带淫゛_ 提交于 2019-11-28 14:10:22
I'm trying to decode the data bytes from a GIF87a raster data stream. I'm unsure of how to read the LZW variable length codes (and how LSB...least significant byte first fits in this). The raster data stream starts as follows (in hex): 06 6b 40 86 70 48 2c 1a 8f 44 4b 44 22 89 58 8e 10 c7 e1 80 06 ->code size of 6 6b ->block byte count of 107 40 ->clear code (2^6) which is 64 in decimal or 40 in hex 86 -> start of actual data GIF87a spec: http://www.w3.org/Graphics/GIF/spec-gif87.txt The raster stream should have indexes that point to the global map (or to a parent in the LZW tree)...but I'm

LZW Compression In Lua

由 喜夏-厌秋 提交于 2019-11-27 08:36:04
问题 Here is the Pseudocode for Lempel-Ziv-Welch Compression. pattern = get input character while ( not end-of-file ) { K = get input character if ( <<pattern, K>> is NOT in the string table ){ output the code for pattern add <<pattern, K>> to the string table pattern = K } else { pattern = <<pattern, K>> } } output the code for pattern output EOF_CODE I am trying to code this in Lua, but it is not really working. Here is the code I modeled after an LZW function in Python, but I am getting an

Decode data bytes of GIF87a raster data stream

由 白昼怎懂夜的黑 提交于 2019-11-27 08:17:23
问题 I'm trying to decode the data bytes from a GIF87a raster data stream. I'm unsure of how to read the LZW variable length codes (and how LSB...least significant byte first fits in this). The raster data stream starts as follows (in hex): 06 6b 40 86 70 48 2c 1a 8f 44 4b 44 22 89 58 8e 10 c7 e1 80 06 ->code size of 6 6b ->block byte count of 107 40 ->clear code (2^6) which is 64 in decimal or 40 in hex 86 -> start of actual data GIF87a spec: http://www.w3.org/Graphics/GIF/spec-gif87.txt The
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