GIF is an abbreviation for Graphics Interchange Format. It is a bitmap image format that allows file compression without degrading the visual quality. It is introduced by CompuServe in 1987; the format is now most preferred and commonly used on World Wide Web for its wide support as well as portability. It is often referred as an animated raster graphics file.
The GIF format supports up to 8 bits per pixel for each image that allows a single image to reference its own palette, which contains up to 256 different colors. These colors are chosen from the 24-bit RGB color space. It also supports animations and even allows a separate palette of up to 256 colors for each frame.
GIF files make use of LZW, “Lempel-Ziv-Welch” data compression which is a lossless compression technique to reduce the size of the file. GIFs are suitable for sharp-edged line art (such as logos) that uses a limited number of colors. Moreover, this GIF format can also be used to store low-color sprite data for games or for low resolution film clips and small animations.
File Extension: .gif
Mime Type: image/gif
Versions of GIF
There are two versions of the GIF format; they are GIF 87a and GIF 89a:
Areas of application: Drawings (technical or line-drawings), Sketches, Diagrams, Icons, Thumbnails, Logos etc.
Features of GIF format
Limited color palette: A GIF image can contain 2, 4, 8, 16, 32, 64, 128 or 256 colors that are stored in a color palette within the image file. Every color used in the GIF color table will be named in RGB values, where each value has a range of 0 to 255. However, CMYK colors are not possible in GIF. Even though the GIF format has access to more than 16.8 million colors, but only a maximum of 256 can be referenced within a single GIF image.
Dithering: This technique is used to create an illusion of larger color depth by blending a smaller number of colored “dots” together. Actually, dithering is not really a feature of GIF; it is simply a technique that is often used within GIF images.
Transparency: Transparency is a feature of the GIF89a format which allows the specification of one of the colors in the palette to be ignored while processing the image for your display device. This feature works well on the internet, but it is not supported by layout applications, which rely on EPS-images or PSD-files.
Interlacing: Interlacing is another web-specific feature of GIF. It is a mechanism that makes the images to appear faster on-screen. It first displays the lower version of an image and gradually shows the full version. Physically, an interlaced GIF has scanlines that are stored in an unusual order.
Animation: The GIF89a specifications add a few enhancements to its file header that facilitates the browsers such as Netscape, Mozilla etc. to display multiple GIF images in a timed or looped sequence.
Resolution: Even though GIF images do not require any specific resolution, as most GIF images have a resolution between 72 and 90 dpi, which is ideal for on-screen viewing.
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