GIF (*.gif)

Graphic Interchange Format. Raster graphics image file type.

8-Bit-per-pixel bitmap image format. This format is widely used on the internet due to wide support and portability. This format is not suitable for continuous coloured images such as photographs as it has a limited colour palette (256), it is better suited for graphics with solid coloured areas.

GIF is a lossless data compression method known as the Lempel-Ziv-Welch (LZW) compression technique, it reduces file size without being detrimental to image quality and leaves sharp edges clearly defined unlike JPEGs. It compresses at ratios between 3:1 and 5:1.

The GIF format was developed in 1987 by Compuserve who needed a platform independent image format suitable for transfer across slow connections. Currently there are 2 standard GIFs 87a and 89a. Enhancements to 89a included interlacing, ability to define one colour to be transparent and ability to store multiple images in one file to create basic animations.

Portable Network Graphics (PNG) is a popular alternative to GIF, this is not limited to a 256 colour palette and is better compressed, however PNG can only be used for still images and not animations.


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