Overview of BMP, GIF, JPEG, PNG, and other image formats

BMP format
BMP is short for bitmap. It is a standard image file format in windows and can be supported by multiple Windows applications. With the popularity of the Windows operating system and the development of a wide range of Windows applications, the BMP bitmap format is widely used. This format is characterized by rich image information and almost no compression, which leads to its inherent disadvantage-occupying too much disk space. Therefore, BMP is currently popular on a single machine.
　　
GIF format
GIF is the abbreviation of Graphics Interchange Format. As the name suggests, this format is used to exchange images. As a matter of fact, in the 1980s S, CompuServe, a famous online information service organization in the United States, developed this GIF image format to address the limitations on network transmission bandwidth at that time.
The GIF format features a high compression ratio and less disk space. Therefore, this image format is widely used. The original GIF is simply used to store a single static image (gif87a). Later, with the development of technology, several static images can be stored simultaneously to Form Continuous animation, at that time, it became one of the few formats supporting 2D animation (gif89a). In gif89a images, a transparent area can be specified, so that the image has an extraordinary display effect, which makes the GIF more elegant. Currently, most color animation files on the Internet are in this format, also known as gif89a.
In addition, considering the actual situation in the network transmission, the GIF image format also adds the gradual display mode, that is, during the image transmission process, the user can first see the approximate outline of the image, then, as the transmission process continues, we gradually see the details of the image, so as to adapt to the user's viewing psychology "from haZy to clear. Currently, most color animation files on the Internet are in this format.
The GIF format can only store up to 8-digit digital images, so it can only use up to 256 colors to represent objects, and it cannot help Complex Color objects. Even so, this format is still widely used on the Internet, which is inseparable from the advantages of short GIF image files, fast Downloading speed, and the composition of animations with many images of the same size.
　　
JPEG format
JPEG is also a common image format, which was developed by the Joint photo expert group (joint photographic Experts Group) and named "ISO 10918-1". JPEG is just a common concept. The extension of the ZIP file is .jpg or .jpeg. Its compression technology is very advanced. It uses lossy compression to remove redundant images and color data, and obtains a very high compression ratio while displaying rich and vivid images. In other words, that is, you can use the least disk space to get better image quality. Since the JPEG format compression algorithm uses the brightness color between balanced pixels to compress, it is more conducive to displaying images with gradient colors and without clear outlines.
At the same time, JPEG is also a flexible format with the ability to adjust image quality, allowing you to use different compression ratios to compress such files, for example, we can compress up to 1.37mb BMP bitmap files to 3kb. Of course, we can find a balance between image quality and file size.
Due to the excellent quality and outstanding performance of JPEG, it is also widely used, especially in online and optical disc reading. Currently, all types of browsers support the JPEG image format. Because the JPEG format has a small file size and fast download speed, the web page may provide a large number of beautiful images in a short download time, at the same time, JPEG becomes the most popular image format on the network.
When you save an image in JPEG format, Photoshop provides a variety of save options. You can choose to use different compression ratios to compress the JPEG file, that is, the compression ratio and image quality are optional.
　　
2000-01 format
JPEG 2000 is also developed by the JPEG organization. It has a formal name called "ISO 15444". Compared with JPEG, it provides a new generation of Static Image Compression Technology with higher compression ratio and more new features.
As an upgraded version of JPEG, the compression ratio is about 30% higher than that of JPEG. Different from JPEG, MPEG-4 supports both lossy and lossless compression, while JPEG supports only lossy compression. Lossless compression is very useful for saving some important images. One of the most important features of 2000's is that it can achieve progressive transmission, which is similar to the GIF's "gradual display", that is, first transmitting the image contour and then gradually transmitting data, continuously improve the image quality, so that the image can be clearly displayed from the haze, instead of being slowly displayed from top to bottom like the current JPEG.
In addition, it also supports the so-called "regions of interest" feature. You can specify the compression quality of the areas of interest on the image, or extract the specified part first. Compared with JPEG, JPEG 2000 has obvious advantages and is backward compatible. Therefore, the traditional JPEG format is just around the corner.
It can be applied to traditional JPEG markets, such as scanners and digital cameras. It can also be applied to emerging fields, such as network transmission and wireless communication.
　　　　　　
Tiff format
Tiff (TAG Image File Format) is a widely used image format in Mac. It was jointly developed by Aldus and Microsoft. It was originally designed to store scanned images across platforms. It features a complex image format and a large amount of storage information. Because it stores a large amount of fine-grained information on images and improves the quality of images, it is very helpful for copying the original version.
The compression format can be compressed or non-compressed, and the LZW lossless compression solution can be used for storage. However, due to the complex structure and poor compatibility of TIFF, your software may not be able to correctly identify TIFF files (most of the software has solved this problem ). At present, it is very convenient to transplant TIFF files on Mac and PC. Therefore, tiff is now one of the most widely used image file formats on computers.
　　
PSD format
This is the specialized format Photoshop document (PSD) for image processing software Photoshop of the famous Adobe Company ). PSD is actually a "Draft image" for Photoshop graphic design. It contains samples of various layers, channels, masks, and other designs, so that the last design can be modified when the file is opened next time. In the various image formats supported by Photoshop, PSD is much faster to access than other formats and has powerful functions.
　　　　
PNG format
PNG (Portable Network Graphics) is a new network image format. At the end of 1994, unysis announced that the GIF has a patented compression method, requiring the author of The GIF software to pay a certain fee, which prompted the birth of a free PNG image format. At the beginning, PNG combined with GIF and jpg, and planned to replace these two formats. In October 1, 1996, PNG was proposed to the international network alliance and was recognized by the standards. In addition, most of the drawing software and browsers began to support the browsing of PNG images. From then on, the PNG image format was vibrant.
PNG is currently the most authentic format. It draws on the advantages of GIF and jpg, and has rich storage formats, with both GIF and jpg color modes; another feature of PNG compresses image files to the limit to Facilitate network transmission, while retaining all information related to image quality because PNG uses lossless compression to reduce the file size, this is different from sacrificing image quality in exchange for JPG with a high compression ratio. Its third characteristic is that the display speed is very fast, you only need to download 1/64 of the image information to display low-resolution preview images. Fourth, PNG also supports the creation of transparent images, which are useful when making web images, we can set the image background to transparent, and use the color information of the webpage to replace the transparent color, so that the image and the webpage background can be harmoniously integrated.
The disadvantage of PNG is that it does not support animation effects. If it can be enhanced in this aspect, it can completely replace GIF and JPEG. The default format of Macromedia fireworks is PNG. Nowadays, more and more software are beginning to support this style, and it is becoming increasingly popular on the Internet.
　　
CDR format
The CDR format is the specialized Graphic File Format of the famous drawing software CorelDraw. Since CorelDraw is a vector graphics rendering software, CDRS can record the attributes, locations, and pages of a file. However, it is less compatible and can be used in all CorelDraw applications, but other image editing software cannot open such files.
　　
Swf format
With Flash, we can create an animation with the suffix SWF (Shockwave format). The animated images in this format can use a relatively small volume to express rich multimedia forms. In terms of image transmission, you do not have to wait until all files are downloaded for viewing. Instead, you can download and view images. Therefore, it is particularly suitable for network transmission, especially when the transmission rate is poor, it can also achieve better results. It turns out that SWF has been widely used in Web pages for Multimedia Demonstration and interactive design. In addition, SWF animation is made by vector technology, so no matter how many times the screen is enlarged, the screen will not be damaged. In summary, swf format works are favored by more and more web designers for their high-definition image quality and small size. They are also becoming the mainstream in Webpage animation and webpage image design and production, it has become a de facto standard for online animation.
　　
SVG format
SVG can be regarded as the most popular image file format at present. Its English name is Scalable Vector Graphics, which means a scaled vector image. It is based on XML (Extensible Markup Language) and developed by the World Wide Web Consortium (W3C. Strictly speaking, it should be an open standard vector graphics language that allows you to design exciting, high-resolution web graphics pages. Users can use code to describe images directly. They can use any text processing tool to open SVG images and change some code to enable image intercommunication, and can be inserted into HTML at any time for viewing through a browser.
It provides the advantages that GIF and JPEG are currently popular on the Internet. They can be scaled up at will, but will never be at the cost of image quality; words are editable and searchable in SVG images. On average, SVG files are much smaller than JPEG and GIF files, so they are quickly downloaded.
　　　　　　
Other non-mainstream image formats:
PCX format
The PCX format is a format developed by zsoft when developing the image processing software paintbrush. It is a compressed format that occupies less disk space. Because the format takes a long time and has the ability to compress and fully color, it is still quite popular.
　　
DXF format
Autodesk Drawing exchange format is a vector file format in AutoCAD. It stores files in ASCII Code and is very precise in the aspect of graphics size. Many applications support input and output in the DXF format.
　　
WMF Format
WMF (Windows Metafile format) is a common primitive file format in windows, which is a vector file format. It has the characteristics of short files and pattern styling. The entire image is often spliced by an independent component, and its image is often rough.
　　
EMF format
EMF (Enhanced Metafile) is a Windows 32-bit extended Metafile format developed by Microsoft to make up for the lack of WMF. It also belongs to the Vector file format, the objective is to make the Metafile more acceptable.
　　
LIC (FLI/FLC) Format
The Flic format was developed by Autodesk. Flic is the collective name of FLC and FLI: FLI is the initial animation file format based on 320x200 resolution, FLC adopts a more efficient data compression technology, so it has a higher compression ratio than fli, and its resolution has also improved a lot.
　　
EPS format
Encapsulated postscript (EPS) is a rare format for PC users, while many Mac users use it. It is an ascii code file format described in PostScript Language and is mainly used for typographical, print, and other output work.
　　　　　　
TGA format
The TGA (tagged graphics) file is an image file format developed by truevision for its display card. It has been accepted by the image and image industry internationally. The structure of the TGA is relatively simple. It is a common format of graphics and image data, which has a great impact on the multimedia field. It is a preferred format for computer-generated image conversion to television.
　　　　　　
PICT format
The Pict format is developed based on the quickdraw screen language of the Mac machine and is a local image format used on the Mac machine. If QuickTime software is installed on the Mac machine, you can use JPEG compression to compress the PICT image. However, it should be known that the JPEG compression in QuickTime format may destroy your image more than the files saved in normal JPEG format. For this reason, the file saved as JPEG is clearer in most cases than the PICT file. The reason for using the Pict format is that it allows people without image editing software to see your images. You can open PICT files in simpletext, Microsoft Word, and other word processing software.