lzw

问题 I have read that lz4 algorithm is very fast and has pretty good compression. But in my test app compressed text is larger than the source text. What is the problem? srand(time(NULL)); std::string text; for (int i = 0; i < 65535; ++i) text.push_back((char)(0 + rand() % 256)); cout << "Text size: " << text.size() << endl; char *compressedData = new char[text.size() * 2]; int compressedSize = LZ4_compress(text.c_str(), text.size(), compressedData); cout << "Compressed size: " << compressedSize <

问题 I have read that lz4 algorithm is very fast and has pretty good compression. But in my test app compressed text is larger than the source text. What is the problem? srand(time(NULL)); std::string text; for (int i = 0; i < 65535; ++i) text.push_back((char)(0 + rand() % 256)); cout << "Text size: " << text.size() << endl; char *compressedData = new char[text.size() * 2]; int compressedSize = LZ4_compress(text.c_str(), text.size(), compressedData); cout << "Compressed size: " << compressedSize <

问题 I am implementing a LZW algorithm in C++. The size of the dictionary is a user input, but the minimum is 256, so it should work with binary files. If it reaches the end of the dictionary it goes around to the index 0 and works up overwriting it from there. For example, if i put in a alice in wonderland script and compress it with a dictionary size 512 i get this dictionary. But i have a problem with decompression and the output dictionary from decompressing the compressed file looks like this

来源： https://stackoverflow.com/questions/12169429/is-there-a-trick-to-creating-an-animated-gif-of-tv-static-that-will-allow-it-to

问题 Given the input from example1 on page http://michael.dipperstein.com/lzw/#example1, I am unable to get the correct result: #include <stdio.h> #include <stdlib.h> #include <string.h> #include "lzw.h" void print_hex(unsigned char str[], int len) { int idx; for (idx = 0; idx < len; idx++) printf("%02x", str[idx]); } int main() { FILE *fpIn; /* pointer to open input file */ FILE *fpOut; /* pointer to open output file */ FILE *fptr; char test_str_lzw[] = { "this_is_his_thing" }; fptr = fopen("lzw

问题 I'm looking for a LZW compression algorithm in C# that takes a "string" and returns a string. I've googling for hours and all I've found use MemoryStream, BinaryWriters, etc. I just want to be able to do something like: string _data = "12345"; string _result = CompressToLZW(_data); and then pass that string via Ajax to the browser. I already have the LZW decompression algorithm for javascript (http://rosettacode.org/wiki/LZW_compression#JavaScript) Thanks.- UPDATE: This is the code I'm using

问题 I'm writing a program for an assignment which has to implement LZW compression/decompression. I'm using the following algorithms for this: -compression w = NIL; while ( read a character k ) { if wk exists in the dictionary w = wk; else add wk to the dictionary; output the code for w; w = k; } -decompression read a character k; output k; w = k; while ( read a character k ) /* k could be a character or a code. */ { entry = dictionary entry for k; output entry; add w + entry[0] to dictionary; w

问题 I have a database which contains picture data stored as a binary blob. The documentation says the data is encoded using LZW. I thought that I could decode it using the Zip or GZip input streams found in the Java library, but it didn't work - I got an exception that said the format of the data is not correct. From what I've read, the library uses DEFLATE, which is not LZW. Also, I've read about some licensing problems for using the LZW algorithm. What can I use to decode the data? Is there a

问题 I am attempting to add non-interlaced GIF images other than 8-bit to a PDF document without having to fully decode the bitstream using PDF::Create for Perl. The LZWDecode algorithm that is part of the PDF standard requires all images to have a minimum LZW code size of 8-bits, and PDF::Create is hard-coded to only embed 8-bit images. So far, I have adapted the image loader from PDF::Create to read a 5-bit image and to fully decode the LZW stream. I am then able to use the encoder algorithm

问题 Can anybody give pointers how I can implement lzw compression/decompression in low memory conditions (< 2k). is that possible? 回答1: The zlib library that everyone uses is bloated among other problems (for embedded). I am pretty sure it wont work for your case. I had a little more memory maybe 16K and couldnt get it to fit. It allocates and zeros large chunks of memory and keeps copies of stuff, etc. The algorithm can maybe do it but finding existing code is the challenge. I went with http:/