lzw

Why using unix-compress and go compress/lzw produce different files, not readable by the other decoder?

由 走远了吗. 提交于 2019-12-13 00:19:17
问题 I compressed a file in a terminal with compress file.txt and got (as expected) file.txt.Z When I pass that file to ioutil.ReadFile in Go, buf0, err := ioutil.ReadFile("file.txt.Z") I get the error (the line above is 116): finder_test.go:116: lzw: invalid code I found that Go would accept the file if I compress it using the compress/lzw package, I just used code from a website that does that. I only modified the line outputFile, err := os.Create("file.txt.lzw") I changed the .lzw to .Z . then

How to detect codeword length for LZW Decoding

由 佐手、 提交于 2019-12-12 03:02:52
问题 I'm writing a general LZW decoder c++ program and I'm having trouble finding documentation on the length (in bits) of codewords used. Some articles I've found say that codewords are 12bits long, while others say 16bits, while still others say that variable bit length is used. So which is it? It would make sense to me that bit length is variable since that would give the best compression (i.e. initially start with 9 bits, then move to 10 when necessary, then move to 11 etc...). But I can't

ArrayList<Byte> vs String in Java

由 房东的猫 提交于 2019-12-10 15:21:25
问题 I am implementing the LZW algorithm. I have implemented it for strings and text files successfully and am currently modifying my code to work with binary files, such as images or executables (since I cannot read these files as strings). I have replaced the String type in my code with the ArrayList<Byte> type. My code now compresses and decompresses binary files correctly, however it is at least 10x slower! This is unacceptable in a compression application where speed is a critical element.

loop rolling algorithm

由 你离开我真会死。 提交于 2019-12-10 09:41:51
问题 I have come up with the term loop rolling myself with the hope that it does not overlap with an existing term. Basically I'm trying to come up with an algorithm to find loops in a printed text. Some examples from simple to complicated Example1 Given: a a a a a b c d I want to say: 5x(a) b c d or algorithmically: for 1 .. 5 print a end print b print c print d Example2 Given: a b a b a b a b c d I want to say: 4x(a b) c d or algorithmically: for 1 .. 4 print a print b end print c print d

LZW Data Compression In Lua [duplicate]

由 Deadly 提交于 2019-12-08 13:43:18
问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: LZW Compression In Lua Here is my code for compressing data in Lua using the LZW compression method. My problem is that the function is returning the character 'T', instead of returning the full compressed string 'TOBEORNOTTOBEORNOT'. Thanks! function compress(uncompressed) local dict_size = 256 local dictionary = {} w = "" result = {} for i = 1, #uncompressed do local c = string.sub(uncompressed, i, i) local wc

A Java library to compress (e.g. LZW) a string

由 回眸只為那壹抹淺笑 提交于 2019-12-08 05:23:10
问题 Apache Commons Compress works only with archive files (please correct me if I am wrong). I need something like MyDB.put(LibIAmLookingFor.compress("My long string to store")); String getBack = LibIAmLookingFor.decompress(MyDB.get())); And LZW is just an example, could be anything similar. Thank you. 回答1: You have a plethora of choices - You can use the java.util.Deflater for the Deflate algortihm, try { // Encode a String into bytes String inputString = "blahblahblah??"; byte[] input =

Use Perl to Add GIF Image Other Than 8-bit to PDF

由 ≯℡__Kan透↙ 提交于 2019-12-08 01:25:32
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 from PDF::Create to re-pack the image as 8-bit. What I'd like to do is to eliminate the memory-intensive

Lossless compression method to shorten string before base64 encoding to make it shorter?

由 孤人 提交于 2019-11-30 16:50:07
问题 just built a small webapp for previewing HTML-documents that generates URL:s containing the HTML (and all inline CSS and Javascript) in base64 encoded data. Problem is, the URL:s quickly get kinda long. What is the "de facto" standard way (preferably by Javascript ) to compress the string first without data loss? PS; I read about Huffman and Lempel-Ziv in school some time ago, and I remember really enjoying LZW :) EDIT: Solution found; seems like rawStr => utf8Str => lzwStr => base64Str is

How can I do LZW decoding in Java?

由 前提是你 提交于 2019-11-29 07:20:02
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 library? Do I have to implement it myself? What about the licensing problems? Stephen C Here are a

LZW compression/decompression under low memory conditions

由 ⅰ亾dé卋堺 提交于 2019-11-28 19:52:53
Can anybody give pointers how I can implement lzw compression/decompression in low memory conditions (< 2k). is that possible? 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://lzfx.googlecode.com The decompression loop is tiny, it is the older lz type compression that relies on the
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