Image files and formats

GIF and JPEG graphic file format are the most popular for web development.

The GIF

Gif (graphic interchange format) is the most widely used Web graphic file format. Gif compression is 8-bit and it contains a maximum of 256 colors (Can also displays images in Black&white and gray scale).
GIFs are better suited for graphics with big areas of solid color such as icons and logos and black and white images. However the 8-bit compression and maximum of 256 colors is not suitable for photographic images. jpeg format is widely used for photo's.

Image Compression
Images which are used for the web should be as small as possible in terms of file size (the larger the file the longer it takes to download across the internet. One of the common ways to reduce the file size is to reduce the number of colors it holds).

Transparent Gifs
The GIF transparent color extension allows an image to specify a transparent color, which can then be displayed as the same color as the background on which the image is to be displayed.

Interlaced Gif image
Interlaced images appear quickly at low resolution first (entire image) and then gradually to full resolution once fully downloaded.

The JPEG

The JPEG format (Joint Photographic Experts Group) has been designed for photographic or high color quality images. JPEG is 24 bits (supports up to 16.7 million colors). As a result, JPEGs are ideal for photographs.

PNG

PNG (Portable Network Graphic) Ideal fomat for image compression However, many older browsers (I.E. 4 and Netscape 4 or older) do not support the format without using plug-ins. PNG compression can be 8-bit, 24-bit, or 32-bit, can contain transparency.

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