Computers store pictures in two main ways:
1. lines and blocks of colour
2. dots of colour
1. Windows metafiles
(WMF) are made of lines and blocks. They are used for cartoon type pictures and symbols in Writing with symbols
2. Bitmaps
(BMP) are made up of coloured dots or pixels. They are used for photographic images, for example pupils pictures in Writing with symbols.
Bitmaps are usually very large, and the size of the file increases enormously as the size of picture increases.
Jpegs are similar to Bitmaps. They are very good for colour photographic images. Jpegs are compressed files so they are much smaller than Bitmaps. Using Jpegs you can choose what percentage of detail the picture is stored (and what size of the picturefile). Jpegs at 80% are a good balance between file size and picture quality.(Jpegs at less than 10% are unrecognisable).
Another common picture format are Giffs. These are generally used for pictures on the World Wide Web.