Summary of example codes about compression algorithms

Preface The LZ77 algorithm is a lossless compression algorithm published by Israeli Abraham Lempel in 1977. LZ77 is a typical dictionary-based compression algorithm, and many current compression technologies are based on LZ77. In view of its status in the field of data compression, this article will introduce its principles in detail with pictures and source code. Principle introduction: First introduce a few professional terms. 1. lookahead buffer (I don’t know how to express it in Chinese, temporarily called the area to be encoded): the area waiting for encoding 2. search buffer: the area that has been encoded, search buffer 3. Sliding window: a window of specified size, including "search" Buffer" (left) + "Area to be encoded" (right) Next, the specific encoding process is introduced: In order to encode the area to be encoded, the encoder searches in the search buffer of the sliding window until a matching string is found. The distance between the starting string of the matching string and the buffer to be encoded is called the "offset value", and the length of the matching string is called the "matching length". When encoding, the encoder will keep searching in the search area until it finds the maximum matching string and outputs (o, l), where o is the offset value and l is the matching length. Then window

1. Detailed graphic explanation of LZ77 compression algorithm encoding Python implementation principle

Introduction: Preface The LZ77 algorithm is a lossless compression algorithm published by Israeli Abraham Lempel in 1977. LZ77 is a typical dictionary-based compression algorithm, and many current compression technologies are based on LZ77. In view of its status in the field of data compression, this article will introduce its principles in detail with pictures and source code. Principle introduction: First, introduce a few professional terms. 1.lookahead buffer (I don’t know how to express it in Chinese, temporarily called the area to be encoded): the area waiting for encoding 2. search buffer: the area that has been encoded, search buffer 3. Slide...

2. LZW Compression Algorithm

Introduction: LZW Compression Algorithm

3. a The perfect PHP ZIP compression code_PHP tutorial

#Introduction: A perfect PHP ZIP compression code. This program can quickly compress our files into the zip or rar compression package we want using the PHP compression class. The suffix name can be customized. The compression algorithm comes from a foreign website

4. [GD] Generate images in bmp format (imagebmp)_PHP tutorial

Introduction: [GD] Generate images in bmp format (imagebmp). There is no function to generate bmp images in the GD library, so I wrote one myself. This function also has a compression algorithm that I haven't written yet, but it is enough. Students who need it can take a look. int image

5. Compressed output gzip_PHP tutorial

#5. Compression output gzip_PHP tutorial

Introduction: PHP program acceleration exploration Compress the output with gzip. Using the mod_gzip module in Apache, we can use the gzip compression algorithm to compress the web content published by the Apache server and then transmit it to the client's browser. If it is plain text

6. A perfect PHP ZIP compression code

Introduction: A perfect PHP ZIP compression code. This program can quickly compress our files into the zip or rar compression package we want using the PHP compression class. The suffix name can be customized. The compression algorithm comes from a foreign website

7. [GD] Generate images in bmp format (imagebmp)

Introduction: [GD] Generate images in bmp format (imagebmp). There is no function to generate bmp images in the GD library, so I wrote one myself. This function also has a compression algorithm that I haven't written yet, but it is enough. Students who need it can take a look. int image

8. Make remote transfer of large files faster

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Introduction: I did the test on two virtual machines. If you use traditional SCP remote copy, the speed is relatively slow, as shown in the figure: lz4 compression is now used for transmission. LZ4 is a very fast lossless compression algorithm with a compression speed of 300MB/S on a single core and is scalable

##9. rman backup optimization ideas

Introduction: This chapter does not talk about the principle of rman backup, but only provides some ideas 1. oracle11g selects the compression algorithm as intermediate; 2. Increase the channel of rman backup. The above two methods can increase CPU utilization and reduce IO. 3. Specify the rate parameter. The sum of the rate and channel should not be greater than the IOPS of the hard disk to avoid causing IO waiting - not finished (please continue to pay attention). Thank you

10. unity3d - Is there a symmetrical compression algorithm between C# (unity) and php?

Introduction: I recently developed a game project using unity on the client side and php on the server side. I want to compress the amount of communication data transmitted between the client and the server. What compression and decompression algorithms are available in Unity? Is there a symmetric compression and decompression API available on the PHP side? Thank you ~

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