Graphics Formats for the World Wide Web

There are hundreds of graphics formats. Almost every graphics program has its own. Some, such as TIFF, also have sub formats and different versions or implementations. Web browsers can only display a few formats, and servers vary in the formats which they provide. The data is transferred in whatever seems to be the “best” format which the client and server have in common.

There are several kinds of graphics files:-

• Raster files (also called bitmapped files) contain graphics information represented as pixels, such as photographic images. These include GIF, PNG, and JPEG.
• Animation formats are usually sequences of raster data.
• Vector files contain data for mathematical operations and are typically used to store line art and CAD information.
• Metafiles may contain either raster or vector graphics data.
• Page Description Languages (PDL) are used to describe the layout of a printed page of graphics and text, e.g. Adobe PDF.
• Multi-dimensional object formats store graphics data as a collection of objects (data and the code that manipulates it) that may be rendered as if seen from any viewpoint.
• Virtual Reality Modeling Language (VRML) is a 3D, object-oriented language used for describing “virtual worlds” hyperlinked within the World Wide Web.
• Multimedia file formats are capable of storing any of the above types of data, often including sound and/or video information.

The HTML specification does not prescribe or limit which graphics format you can use. In practice, your choice will be determined by considerations such as

• the image quality,
• availability in clients,
• the data size (and therefore transfer time),
• requirements for transparency, streaming, or progressive rendering,
• whether the format is an open standard or a commercial one subject to copyright or patent fees.

It is useful to have a standard so that you know that if you support that, you will be able to read from or supply to anyone. Until December 1994, GIF played that role, but at that time Unisys’s pursuit of patent license fees moved it from an open standard into the proprietary domain.