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Pixels

Computer images are made of dots, cells or pixels. Each pixel takes on a single colour. The pixels are small enough that they are not normally seen. By zooming in on an image with a computer program the individual pixels can be made obvious.

Polly Woodside
The normal image.	A region of the image at 4x zoom showing the individual pixels.

	Lines and edges that are nearly vertical or nearly horizontal can suffer from the stair-case effect (left). The eye easily latches onto it because there is a regular error in the way the pixels approximate the intended continuous lines. The lines in the picture of the ship (above) do not suffer from this defect because intermediate colour values are used where a line, or edge, partially crosses a pixel. This effect is called anti-aliasing. It happens naturally on scanned photographs and is added to some computer-generated images to improve their appearance.

Polly Woodside

The normal image.

A region of the image at 4x zoom showing the individual pixels.

Lines and edges that are nearly vertical or nearly horizontal can suffer from the stair-case effect (left). The eye easily latches onto it because there is a regular error in the way the pixels approximate the intended continuous lines.

The lines in the picture of the ship (above) do not suffer from this defect because intermediate colour values are used where a line, or edge, partially crosses a pixel. This effect is called anti-aliasing. It happens naturally on scanned photographs and is added to some computer-generated images to improve their appearance.