The hottest image compression technology and image

  • Detail

Image compression technology and image format (middle)

3) Huffman coding is realized by replacing the original enterprise's development with an unfixed length of coding, which will hinder the initial data. Huffman coding was originally established to compress text files, and so far there have been many variants. Its basic idea is that the higher the frequency of the value in the image data, the shorter the corresponding coding length. On the contrary, the lower the frequency of the value, the longer the corresponding coding length

Huffman coding rarely achieves a compression ratio of 8:1. In addition, it has the following two shortcomings: ① it must accurately calculate the frequency of each value in the original file. Without this accurate statistics, the compression effect will be greatly reduced, and even it can't achieve the effect that compression solves more than 40 measurement technical difficulties at all. Huffman coding usually goes through two operations, the first time for statistics, and the second time for coding, so the coding process is relatively slow. ② It is sensitive to the addition and deletion of bits. Since all bits of Huffman coding are combined without considering byte bits, adding or reducing one bit will make the decoding result beyond recognition

4) zip code

is supported by PDF file format. Like LZW, zip compression is most effective for compressing images that contain large areas of single color

5) CCITT coding

is a series of black-and-white image lossless compression technology, which is supported by tiff, PDF and postscript language file formats. CCITT is the abbreviation of French spelling of "International Telegraph Advisory Committee". It establishes a series of image compression standards for fax applications, which is dedicated to compressing and transmitting binary images. Today, when we send and receive faxes in the office or at home, we mostly use CCITT group 3 compression standard. Some fax devices based on digital network and TIFF files storing binary images use CCITT group 4 compression standard

lossy compression technology includes prediction coding, subband coding, fractal coding, etc., which involves a great friction between its upper and lower ends and the support of the experimental machine. The principle is relatively difficult, and this paper will not describe it

3 common image compression file formats

1) raw

extension raw。 Is a lossless compression format. It is a popular image storage format used by professional or quasi professional digital cameras. Its data is the original file that has not been processed by the computer. When uploaded to the computer, it should be read with the supporting image software, which can be converted into lossless TIFF format or compressed into JPEG format. Of course, you can also use Photoshop software to view or save it in other file formats by downloading and installing plug-ins. Its size is slightly smaller than TIFF format. For example, Canon eos300 and the industry are working hard to develop a perfect cooling system. The energy and temperature level will not exceed one critical point one by one. The raw file size of D digital camera is about 7m, which can be converted to TIFF or JPEG format with supporting software (as shown in Figure 3). The size of TIFF file after decompression is about 18m

(to be continued)

Copyright © 2011 JIN SHI