BIT‐MAPPED GRAPHICS

Computers can represent pictures as sets of dots or pixels. A picture created in this way is called a bit‐ mapped graphic.

At its simplest a dot can be switched on or off. This allows a black and white image to be produced:

The more dots there are, the higher the resolution of the picture. A picture with a high resolution will be clearer than a picture with a low resolution:

Close up, the dots are quite obvious. From a distance, the dots don't show as obviously.

In a colour picture, more bits are needed to represent each pixel. For a high resolution colour image, this can lead to huge file sizes.

Digital photographs are bit‐mapped images. From a camera with a high count of mega pixels, the file size can be too big to upload to some sites, e.g. social networking or picture sharing, so the files have to be compressed.

IMAGING SOFTWARE

Images are easy to change when they're in a bitmapped form. There are lots of image editors available to produce effects such as changing colours and transforming images in various ways.

Although images can be changed for artistic purposes, image editors can also be used by criminals, for example by altering images for passport photographs.

Some graphics software is so good that it can be impossible to tell if a transformed image is genuine or not. Images can be gradually changed from an original to another different image, showing intermediate stages.

This is called morphing.

Most bit‐mapped graphics packages have a range of tools that achieve a wide range of effects.