Introduction of GIF (The Graphics Interchange Format) Image
The Graphics Interchange Format is known as GIF. GIF is the most widely supported image format on the web.There are two types of GIF , GIF 87 and GIF 89a.This image format is introduced by Compuserve. Both forms of GIF support 8-bit (256 color).
Graphics Interchange Format images use a basic form form of compression called run length encoding.This loss less compression works well with large areas of continuous color.When an image is remapped from a large number of colors to a smaller color palette,dithering occurs.The process of the dithering attempts to creat the desired color that is outside of the palette, by taking two or more colors from the palette and placing them in some sort of checkered or speckled pattern in an attempt to visually create the illusion of the original color.
GIF images also support transparency.One bit of transparency is allowed.It means that one color can be set to be transparent.Transparency allows the background that and image is placed upon to show through, making a variety of complex possible.
In Gif image format color reduction is useful to reduce Graphics Interchange Format file size. The main problem with 1 bit transparency is that anti aliasing uses variable colors to blur the jagged edges of an image to smooth things out.Recall that everything that is displayed onscreen is made up of pixels are square.It should therefore be that creating an image that has rounded edges may pose some problems.
There are a variety of solutions to the anti aliasing transparency interaction problem.First you could simply not anti alias the image,but this can produce unwanted jagginess in the image.
GIF images also support a feature called interlacing. Interlacing allows an image to load in a Venetian blind fashion rather that from top to bottom a line at a time.The interlacing effect allows a user to get an idea of what an image looks like before the entire image has downloaded.Avoiding user frustration as images download.While interlacing a GIF image is generally a good idea,occasionally it comes with a downside; interlaced images may be larger that non interlaced images.
So it is a bad idea to use interlacing for images that have text on them because it’s impossible for the text to be read easily until the download is complete.