File Formats

JPEG (Joint Photographic Experts Group)

JPEG is a standard image compression mechanism.JPEG file formats are used quite frequently as they are small in size and have good quality which makes them useful as they are usually only a few hundred Kilobytes. JPEG is used for either full colour (24 bit) or grey-scale digital images. To make a JPEG file a small file size you have to throw some of the image data away. So when you enlarge a JPEG image the quality will not be as good. It will be done by the lossy compression approach. This specific image format is mainly for the web applications and it is quite similar to the GIF file, however the only difference is that the JPEG files store all of its colour data and doesn’t need transparency whereas the GIF files don’t store the colour information. An example of high quality JPEG image.

GIF (Graphics Interchange Format)

GIF is a bitmap file format which allows you to use up to 8 bits per pixel. The colours are chosen from a 24-bit RGB colour space and supports animation. The GIF file type is mainly used for simple graphics or images such as logos with solid areas of colour. An example of animated GIF image below:

PNG

PNGs, or Portable Network Graphics, were created as an alternative to the GIF file format, when the GIF technology was copyrighted and required permission to use. PNGs allow for 5 to 25 percent greater compression than GIFs, and with a wider range of colors. Like GIFs, PNG file formats also support transparency, but PNGs support variable transparency, where users can control the degree to which an image is transparent. The downside to advanced transparency in PNGs is that not all older browsers will display the transparency the same

All documents on your computer is a file and every file on the computer is given a format for you to know what type of file it is and were it would be stored on the computer . For example a word document in Microsoft word appears as .doc. Here is a few examples of a few programes .

• Word documents (.doc)
• Web text pages (.htm or .html)
• Web page images (.gif and .jpg)
• Adobe Postcript files (.ps)
• Adobe Acrobat files (.pdf)
• Executable programs (.exe)