GIF FORMAT

GIF - Graphics Interchange Format

 

The GIF graphic format developed by Steve Wilhite in 1987 has, despite the visual limitations, made a lot of progress compared to modern formats, especially in social media field as well as on many devices such as smartphones as a popular video format.

The CompuServe graphics format supports a maximum of 256 colors including a transparency color and the option of saving individual images with a specific interval in order to display an animation.

The GIF is understood as a synonym for animated short videos, even if they are not technically in this format.

In the 2010s, GIF animations made a comeback on the web to e.g. cinemagraphs and stereograms to create. In May 2015, Facebook (META) also started supporting GIF.

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Format Properties

 

With a GIF, the color information is stored in a color palette containing up to 256 colors. The colors themselves can be freely selected from 256³ ≈ 16.7 million possible color values, but are always reduced to the maximum 256 slots of the GIF palette. This global color palette file also defines, among other things, all frames in an animated GIF.

More complex images such as photos with many different colors must therefore be reduced to 256 colors or less (color quantization) before saving. The color gradients or dithering effects that are created in this way are annoyingly visible, especially with gradients.

The GIF format itself is compressed and considered as non-lossy, but only under the aspect if the total conversion of the original image does not exceed the necessary colors of 256.

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Transparency

 

As of GIF89a, a color entry (a single color) of the stored palette can be defined as transparent. This allows you to let the respective background color shine through at any point. However, this is not to be equated with an alpha channel, since only a single color code is set to be 100% transparent.

With an 8-bit alpha channel, such as that supported by PNG, partial transparency and a softly graduated Antialiasing enabled transition.

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Interlacing

As of GIF87a, GIF supports saving images with interlacing. The image is not transmitted sequentially from top to bottom, but in four passes with increasing progressive resolution. In the past, this method was often used with slow Internet connections.

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More than 256 colors

Already GIF87a offers the possibility to save several individual images, each of which has its own color palette. The transparency can also be used to overlap images in a series in order to reconstruct a composing for a true color GIF. However, true color GIFs have not achieved great popularity and distribution to this day.

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Alternatives

The patent-free PNG format was developed to replace GIF as the single image format on the World Wide Web. PNG offers more options (up to 64-bit color depth), almost always better compression and can save more colors per frame than GIF. The latter is PNG's biggest advantage over GIF. Despite all the technically better options, GIF has prevailed to this day and is the standard for short animation clips in many areas.

SOURCE MORE INFO Wikipedia Graphics Interchange Format