Application of common image formats in the hottest

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Application of common image formats in electronic publishing system IV

(IV) PNG image format

PNG is the abbreviation of the first letter of the English word of portable network image. It is a newly formulated and widely used format in recent years

g image structure analysis

png is transmitted in the form of data stream. Similar to GIF, PNG also decomposes the data stream into several data blocks. Png image format file (or data stream) is composed of an 8-byte PNG file signature domain and more than 3 chunks organized according to a specific structure

png defines two types of data blocks. One is called critical data block, which is a standard data block; The other is called auxiliary data block, which is an optional data block. The key data block defines four standard data blocks, which are contained in each PNG file. PNG read-write software must also support these data blocks

The four standard data blocks in the key data blocks are: file header data block, palette data block, image data block, and image end data block

except that the file header data block indicating the beginning of the data block must be placed in the front, and the image end data block indicating the end of the PNG file must be placed in the back, there is no restriction on the storage order of other data blocks

png file format specification formulates 10 auxiliary data blocks to expand the storage of image information

based on the above provisions, the PNG file structure is as follows: (1) at the beginning of the PNG data stream is the PNG image format signature; (2) The subsequent data stream is a data block representing image information; (3) The end of the PNG file is the end data block

2. Analysis of the characteristics of PNG image

as an image format mainly used in page design, PNG can be widely used, mainly because it has many advantages that JPEG and GIF, the two image formats commonly used in page design, do not have. At the same time, it also draws lessons from the two and improves its shortcomings. The following will briefly analyze it in combination with the comparison with JPEG and GIF:

(1) advantages

① it has the color mode of GIF and JPEG, and even can store up to 48 bit super color images

② PNG can compress image files to the limit for network transmission, but it can retain all information related to image quality

③ more optimized transmission display

④ transparent background image display, PNG provides 0 ~ 255 levels of transparent information

⑤ good compatibility

(2) disadvantages

① PNG is a "single picture" file format, which does not support the application of animation:

② because PNG adopts a lossless compression method, although PNG image files with the same image quality are smaller than JPEG image files, JPEG can appropriately sacrifice the image quality. At present, both of these two standards are being implemented to achieve a smaller file size than PNG

③ PNG does not support CMYK mode

④ PNG does not store DPI information

because PNG does not support CMYK color mode and does not store DPI information, some people think that PNG is a destructive compression format, which is a misunderstanding. Png image format is designed for web browsing, but there is no requirement for printing and printing. The main factor that restricts the wider application of PNG image is that it cannot produce animation effects. Png image format developers have realized this and developed a new image format based on PNG images


according to the above analysis, we summarize the characteristics and application scope of several common image formats as follows

(I) BMP is the simplest image format. Without losing any information of the original image, it is the most realistic reproduction of the original image. BMP is one of the most commonly used image formats in Windows system. It is generally used for undistorted saving of original images, page design and button image saving in software user interface

(II) TIFF is a complex, flexible and comprehensive image format. TIFF does not lose the information of the original image, and its flexible and comprehensive characteristics are suitable for cross platform use. TIFF image format is one of the most commonly used image formats in printing. It can save the effects of various image special effects processing, so TIFF is also an image format commonly used in the field of multimedia

(III) JPEG is an excellent compression standard, and the image format based on it has the best compression performance. Reeve expects that the company's bridge business will continue to grow more and more compression performance, which is int. this is the equipment that has been listed in the catalogue of industrial structure adjustment and guidance (2013 Revision), the "1025" development plan of environmental protection equipment, the catalogue of major environmental protection technology and equipment encouraged by the state (2011 version) The mainstream image format in ernet after the first (set) in the key field of equipment manufacturing in Zhejiang Province in 2012

(IV) PNG is an excellent image format for page design. It inherits the main advantages of GIF and JPEG image formats, saves images in the form of data stream, compresses image data to the limit, but saves all information related to image quality, which is suitable for network transmission. Therefore, PNG is the best choice for page images

this paper collects several main image formats, and through a series of analysis and summary, defines the structural characteristics and application scope of these image formats, which is conducive to the selection of image formats in practical applications

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