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What Is Gif

   
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It was in 1987 when CompuServe first introduced the graphics interchange format to the computer industry. Today, as a result of its wide support and small size, the gif is one of the most common image formats seen on the World Wide Web today. With the ability to support 256 colours from a 24-bit pallet, and up to 8 bits per pixel including index transparency there is no wonder why. The gif image is also able to support animations and can store each frame with any combination of up to 256 colours from that 24-bit pallet per frame including the index transparency.

 

While it suits its perfect in web development just fine as most logos and navigational elements very rarely exceed the 256 colour limitation, for other uses the gif is not always the best choice. It comes down to its allowed colours and irregardless of how many pixels are in the image, it cannot have any more the 256 colours. As a result, use of the graphics interchange format for something like a rich image would result in a rather ugly looking pixelated image that may not even be distinguishable.

After the image is created as a bitmap not exceeding 256 colours, it is then compressed using a lossless compression process termed Lempel-Ziv-Welch or for easier pronunciation LZW can be said instead. This compression process allows the image to be reduced in its overall size without affecting its quality assuming the colour pallet has not been exceeded.

Unlike image formats like the portable networks graphic or PNG, the gif is proprietary due to the fact that the LZW compression method was under a patent which was obtained in 1985. Matter of fact, it was as a result of these patent issues between CompuServe and Unisys which held the LZW patent that led to the creation of the PNG format in 1994. However, those patents in question have since expired.

CompuServe when developing the graphics interchange format decided that they wanted some colour added to their file downloads and wanted to do away with the currently used run-length encoded format or RLE. The RLE was only capable of handling black and white. Since the LZW compression technique was considered to be far superior to that of the RLE, CompuServe developed the gif to make use of it. Furthermore, this is also one of the reasons which made the gif even more popular.

However back in 1987 when gif was first released, it was not known as the graphical interchange format but rather it was called simply 87a. Then in 1989, CompuServe went back and updated the image format adding multiple image streams as well as metadata thus creating 89a. At the time, the only way to tell the difference between the two was to look at the image’s source code in ASCII format where the first line of data would mark it as either GIF89a or GIF87a.

After the Tim Berners-Lee developed the internet as we know it today, the only image formats used on it was either the XBM image or the GIF. Since by that time the GIF89a had already been released, the ability to store multiple images into a single file was already possible which led to people adding short animated gif images on their site. This would become even more popular after the start of the browser wars between Microsoft’s Internet Explorer and the Netscape Navigator because of the development of JavaScript which allowed website counters that made use of the animated gif images to add some excitement to a page.

While most of the world pronounces the gif name using a hard “g” like the one in golf, the developers at CompuServe who developed the graphical interchange format insist that since its inception the “g” was intended to be pronounced with the soft version which sounds more like the “j” in jiffy.

While some visitors to a website may not be happy with them, it is also possible to create a visually three dimensional image making use of the animations. In all simplicity, like taking a standard 3D image with 2 pictures being slightly apart from each other and toed inwards; as long as the main element in the picture is kept in almost the exact same spot then the result of a two-frame loop animation gives off a three dimension look to it.

In its simplest form, the gif is a limited image due to its colour limitations, but since these colours are in fact limited, it allows for the creation of sharp-edged graphics for use on a website as well as being perfectly suited for the development of sprites for computer games.

One of the other benefits of the gif image is that of index transparency. What this means is that a colour can simply be turned off. If your website has a green background and you want to add an image to the page and save some of your colour slots in doing so, you can turn off the particular green that matches the background. However, irregardless of whether the colour is turned on or off, it is using one of the 256 spots.

With the development of the PNG format though, while it may not be completely supported it has been able to be a tough competitor to the gif. The 8-bit PNG is the same as a gif, except that it allows alpha transparency. This PNG format is also supported when other PNGs are not. The alpha transparency though allows for a colour to be partially transparent versus on or off. Furthermore, recent developments have also placed the PNG up against the gif’s animation capabilities with the recent release of the APNG format which also is animated.

Original Authors: Nick
Edit Update Authors: M.A.Harris
Updated On: 09/02/2009


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