What storage format does the gif format belong to?

The gif format belongs to the storage format of "dynamic images". The gif format is a graphics exchange format used to display indexed color images in hypertext markup language; GIF has two versions, GIF87a and GIF89a. The GIF89a version allows one file to store multiple images, realize animation functions, and allow certain Pixels are transparent.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The gif format belongs to the storage format of "dynamic images".

The full name of GIF is Graphics Interchange Format, which can be translated as Graphics Interchange Format. It is used to display indexed color images in Hypertext Markup Language (Hypertext Markup Language) on the Internet and other online service systems. Be widely used. GIF is a public image file format standard, the copyright of which belongs to Compu Serve.

GIF is a bitmap. The general principle of bitmap is: a picture is composed of many pixels, each pixel is assigned a color, and these pixels are combined to form a picture. GIF uses the Lempel-Zev-Welch (LZW) compression algorithm and supports up to 256 colors. Due to this characteristic, GIF is more suitable for pictures with less color, such as cartoon shapes, company logos, etc. If you encounter situations where true colors are needed, the expressive power of GIF will be limited. GIF usually comes with a palette that stores the various colors that need to be used. In web applications, the file size of images will obviously affect the download speed. Therefore, we can optimize the palette according to the characteristics of GIF with palette and reduce the number of colors used in the image (some images cannot use it. colors can be dropped) without affecting the quality of the picture.

The biggest difference between the GIF format and other image formats is that it is completely designed as a public standard. Due to the popularity of the Compu Serve network, many platforms support the GIF format. Compu Serve promotes GIF by distributing format instructions for free, but requires software that uses the GIF file format to include a description of its copyright information.

GIF has two versions: GIF87a and GIF89a.

The GIF87a version was launched in 1987. One file stores one image and strictly does not support transparent pixels; GIF87a uses the LZW compression algorithm, which can compress the image size by 20% while maintaining image quality. to twenty-five.

The GIF89a version is a very distinctive version launched in 1989. This version allows one file to store multiple images, can implement animation functions, and allows certain pixels to be transparent. In this version, the GIF document has been expanded into four blocks: graphics control block, notes, instructions, and application programming interface, and provides support for transparent colors and multi-frame animation.

Among them, GIF89a has made significant improvements in transparent, interlaced and animated GIFs. The first is to support transparency. GIF89a allows some parts of the picture to be invisible. This feature is very important, allowing us to use this feature in some situations to make the edges of the image no longer appear as rectangular borders, but become any shape we want. These transparent areas can be easily generated in Photoshop and Fireworks and exported as GIF images in GIF89a format. Of course, transparency does not mean that the border no longer exists. In fact, it does exist, but it is not displayed. This can make the inserted picture more coordinated with the overall web page.

If you want to read more related articles, please visit PHP Chinese website! !

The above is the detailed content of What storage format does the gif format belong to?. For more information, please follow other related articles on the PHP Chinese website!