GIF is the abbreviation of English Graphics Interchange Format. As the name implies, this format is used to exchange pictures. In fact, this is also the case. In 198s, CompuServe, a famous online information service organization in the United States, developed this GIF image format for the limitation of network transmission bandwidth at that time.
GIF format is characterized by high compression ratio and less disk space occupation, so this image format has been widely used quickly. At first, GIF was simply used to store a single still image (called GIF87a). Later, with the development of technology, several still images can be stored at the same time to form a continuous animation, making it one of the few formats that supported 2D animation at that time (called GIF89a). In GIF89a, transparent areas can be specified to make the image have extraordinary display effect, which makes GIF more beautiful. At present, a large number of color animation files used on the Internet are mostly files in this format, also known as GIF89a format files.
in addition, considering the actual situation in network transmission, the GIF image format also adds a gradual display mode, that is, in the process of image transmission, users can first see the general outline of the image, and then gradually see the details of the image as the transmission process continues, thus adapting to the user's viewing psychology of "from hazy to clear". At present, a large number of color animation files used on the Internet are mostly files of this format.
but GIF has a small disadvantage, that is, it can't store images with more than 256 colors. Nevertheless, this format is still widely used on the Internet, which is inseparable from the advantages of short GIF image files, fast download speed, and animation composed of many image files with the same size.
JPEG format
JPEG is also a common image format, which was developed by Joint Photographic Experts Group and named as "ISO 1918-1". JPEG is just a common name. The extension of JPEG file is. jpg or. jpeg, and its compression technology is very advanced. It uses lossy compression to remove redundant images and color data, and it can show very rich and vivid images at the same time, in other words, it can get better image quality with the least disk space.
At the same time, JPEG is a very flexible format, which has the function of adjusting the image quality, allowing you to compress this file with different compression ratios. For example, we can compress the BMP bitmap file from 1.37MB to 2.3KB at most. Of course, we can find a balance between image quality and file size.
Because of its excellent quality and outstanding performance, JPEG is also widely used, especially on the Internet and CD-ROM. At present, all kinds of browsers support JPEG as an image format, because the file size of JPEG format is small and the download speed is fast, which makes it possible for Web pages to provide a large number of beautiful images in a short download time, and JPEG has naturally become the most popular image format on the network.