Category: Computer/Network gt; gt; Software
Problem description:
Nowadays, pictures and music have many formats when downloading and saving
What is the difference? Which one is better
Analysis:
Let me answer the question about images...
1. BMP format
BMP is the abbreviation of English Bitmap (bitmap). It is a standard image file format in the Windows operating system and can be supported by a variety of Windows applications. With the popularity of the Windows operating system and the development of rich Windows applications, the BMP bitmap format is naturally widely used. The characteristic of this format is that it contains rich image information and almost no compression, but this leads to its inherent shortcoming-it takes up too much disk space. Therefore, BMP is currently more popular on stand-alone machines.
2. GIF format
GIF is the abbreviation of English Graphics Interchange Format. As the name suggests, this format is used to exchange images. In fact, this is also true. In the 1980s, CompuServe, a well-known online information service organization in the United States, developed this GIF image format in response to the limitations of network transmission bandwidth at that time.
The GIF format is characterized by a high compression ratio and less disk space usage, so this image format has quickly become widely used. The original GIF was simply used to store a single still image (called GIF87a). Later, with the development of technology, several still images could be stored at the same time to form a continuous animation, making it one of the few software that supported 2D animation at that time. One of the formats (called GIF89a), and transparent areas can be specified in the GIF89a image to give the image an extraordinary display effect, which makes GIF even more beautiful. Currently, most of the color animation files used on the Internet are in this format, also known as GIF89a format files.
In addition, taking into account the actual situation in network transmission, the GIF image format also adds a gradual display method, that is to say, during the image transmission process, the user can first see the rough outline of the image, and then gradually As the transmission process continues, the details in the image are gradually seen clearly, thereby adapting to the user's viewing psychology of "from hazy to clear". Currently, most of the color animation files widely used on the Internet are files in this format.
But GIF has a small disadvantage, that is, it cannot store images with more than 256 colors. Despite this, this format is still widely used on the Internet, which is inseparable from the advantages of GIF image files, such as short image files, fast download speed, and the ability to use many image files of the same size to compose animations.
3. JPEG format
JPEG is also a common image format. It was developed by the Joint Photographic Experts Group and named "ISO 10918-1" , JPEG is just a common name. The extension of JPEG file is or .jpeg. Its compression technology is very advanced. It uses lossy compression to remove redundant images and color data, obtaining extremely high compression rate while displaying very rich and vivid images. In other words In other words, you can get better image quality with the least disk space.
At the same time, JPEG is also a very flexible format that has the function of adjusting image quality, allowing you to use different compression ratios to compress this kind of file. For example, we can compress a BMP bitmap file of up to 1.37MB. to 20.3KB. 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 on the Internet and CD-ROM readers, where its shadow can certainly be found. At present, all kinds of browsers support the image format JPEG. Because the file size of JPEG format is small and the download speed is fast, it is possible for Web pages to provide a large number of beautiful images in a short download time. At the same time, JPEG has become a natural The most popular image format on the web.
4. JPEG2000 format
JPEG 2000 is also developed by the JPEG organization. It has an official name called "ISO 15444". Compared with JPEG, it has higher compression A new generation of still image compression technology with high efficiency and more new features.
As an upgraded version of JPEG, JPEG2000 has a compression rate about 30% higher than JPEG. Unlike JPEG, JPEG2000 supports both lossy and lossless compression, while JPEG can only support lossy compression. Lossless compression is very useful for saving some important pictures. An extremely important feature of JPEG2000 is that it can achieve progressive transmission, which is similar to the "gradual display" of GIF, that is, the outline of the image is first transmitted, and then the data is gradually transmitted, continuously improving the image quality, so that the image changes from hazy to hazy. To display it clearly, instead of slowly displaying it from top to bottom like the current JPEG.
In addition, JPEG2000 also supports the so-called "region of interest" feature. You can arbitrarily specify the compression quality of the area of ??interest in the image, and you can also choose the specified part to decompress first. JPEG 2000 has obvious advantages over JPEG and is backward compatible, so replacing the traditional JPEG format is just around the corner.
JPEG2000 can be used in traditional JPEG markets, such as scanners, digital cameras, etc., as well as in emerging fields, such as network transmission, wireless communications, etc.
5. TIFF format
TIFF (Tag Image File Format) is a widely used image format in Mac. It was jointly developed by Aldus and Microsoft and was originally intended for cross-platform storage scanning. Designed for image needs. It is characterized by complex image formats and large amounts of stored information. Precisely because it stores a lot of detailed information on the image, the quality of the image can also be improved, so it is very conducive to the copying of originals.
This format has two forms: compressed and non-compressed. The compression can be stored using the LZW lossless compression scheme. However, due to the complex structure and poor compatibility of the TIFF format, sometimes your software may not be able to correctly identify TIFF files (most software has now solved this problem). It is now very convenient to transplant TIFF files on Mac and PC, so TIFF is now one of the most widely used image file formats on microcomputers.
6. PSD format
This is the special format Photoshop Document (PSD) of the famous Adobe image processing software Photoshop. PSD is actually a "draft" for graphic design in Photoshop. It contains various design samples such as various layers, channels, masks, etc., so that the last design can be modified the next time the file is opened. Among the various image formats supported by Photoshop, the access speed of PSD is much faster than other formats, and its functions are also very powerful. As Photoshop becomes more and more widely used, we have reason to believe that this format will gradually become popular.
7. PNG format
PNG (Portable Neork Graphics) is an emerging network image format.
At the end of 1994, Unysis announced that GIF had a patented compression method and required authors who developed GIF software to pay a certain fee, which led to the birth of the free png image format. PNG has combined the strengths of GIF and JPG from the beginning, intending to replace these two formats in one fell swoop. On October 1, 1996, PNG proposed a standard to the International Network Alliance and was recommended and recognized. Most drawing software and browsers began to support PNG image browsing, and the PNG image format has been revitalized since then.
PNG is currently the most distortion-free format. It draws on the advantages of both GIF and JPG. It has rich storage forms and has the color modes of both GIF and JPG. Another feature of it is that it can convert images into The file is compressed to the limit to facilitate network transmission, but it can retain all information related to image quality, because PNG uses lossless compression to reduce the file size, which is different from JPG which sacrifices image quality in exchange for high compression rate. ; Its third feature is that the display speed is very fast, and only 1/64 of the image information can be downloaded to display a low-resolution preview image; Fourth, PNG also supports the production of transparent images, and transparent images are used in the production of web page images. It is very useful when using this method. We can set the image background to be transparent and use the color information of the web page itself to replace the transparent color. This will allow the image and web page background to blend together harmoniously.
The disadvantage of PNG is that it does not support animation application effects. If it can be improved in this regard, it can completely replace GIF and JPEG. The default format of Macromedia's Fireworks software is PNG. Now, more and more software are beginning to support this format, and it is becoming more and more popular on the Internet.
8. SWF format
Using Flash we can create an animation with the suffix SWF (Shockwave Format). Animation images in this format can be produced in a relatively small size. Expressive multimedia forms. In terms of image transmission, you don't have to wait until the file is downloaded before you can watch it. Instead, you can watch it while downloading. Therefore, it is particularly suitable for network transmission, especially when the transmission rate is not good, it can also achieve better results. Facts have also proven this. SWF has now been widely used in WEB pages for multimedia presentation and interactive design. In addition, SWF animation is produced using vector technology, so no matter how many times the picture is enlarged, the picture will not be damaged in any way. To sum up, SWF format works are favored by more and more web designers due to their high-definition quality and compact size. They have also become more and more mainstream in web animation and web image design and production. Currently, they have become the mainstream of web page animation and web image design and production. The de facto standard for animation.
9. SVG format
SVG can be regarded as the most popular image file format at present. Its full English name is Scalable Vector Graphics, which means scalable vector graphics. It is based on XML (Extensible Markup Language) and developed by the World Wide Web Consortium (W3C) alliance. Strictly speaking, it should be an open standard vector graphics language that allows you to design exciting, high-resolution web graphics pages. Users can directly use code to depict images, open SVG images with any word processing tool, make the images interactive by changing part of the code, and insert them into HTML at any time for viewing through a browser.
It provides advantages that the current popular Internet formats GIF and JPEG cannot have: graphic display can be enlarged arbitrarily, but never at the expense of image quality; words remain editable and searchable in SVG images Status; On average, SVG files are much smaller than JPEG and GIF formats, so they download quickly. It is believed that the development of SVG will provide a new image standard for the Web.
Other non-mainstream image formats:
1. PCX format
PCX format is a format developed by ZSOFT when developing the image processing software Paintbrush. It is a compressed format that takes up less disk space. Because this format has been around for a long time and has the ability to compress and full color, it is still relatively popular.
2. DXF format
DXF (Autodesk Drawing Exchange Format) is a vector file format in AutoCAD. It stores files in ASCII code and is very accurate in expressing the size of graphics. Many software support input and output of DXF format.
3. WMF format
WMF (Windows Metafile Format) is a common metafile format in Windows and is a vector file format. It has the characteristics of short files and stylized patterns. The entire graphics is often spliced ??together from various independent components, and the graphics are often rough.
4. EMF format
EMF (Enhanced Metafile) is a Windows 32-bit extended metafile format developed by Microsoft to make up for the shortcomings of using WMF. It is also a vector file. format, its purpose is to make metafiles more acceptable
5. LIC (FLI/FLC) format
The Flic format was developed by Autodesk. FLIC is the combination of FLC and FLI The collective name: FLI is the original animation file format based on 320×200 resolution, while FLC uses more efficient data compression technology, so it has a higher compression ratio than FLI, and its resolution has also been improved a lot.
6. EPS format
EPS (Encapsulated Postscript) is a format less common among PC users, while Apple Mac users use it more. It is an ASCII code file format described in Postscript language and is mainly used for typesetting, printing and other output work.
7. TGA format
TGA (Tagged Graphics) file is an image file format developed by the American Truevision company for its display card. It has been adopted by the international graphics and image industries. accepted. TGA has a relatively simple structure and is a universal format for graphics and image data. It has a great influence in the field of multimedia and is the preferred format for converting computer-generated images to television.