Representing Images

Computers store images as collections of tiny dots called pixels. This lesson explains how bitmap images are represented in binary, and the factors that affect image quality and file size.

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What Is a Bitmap Image?

A bitmap image is made up of a grid of pixels (picture elements). Each pixel is a single coloured dot. When you zoom into a bitmap image, you can see the individual square pixels.

The computer stores a binary value for each pixel that represents its colour. The entire image is stored as a long sequence of binary values — one for each pixel.

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Key Concepts

Resolution

Resolution refers to the number of pixels in an image, usually expressed as width × height (e.g. 1920 × 1080 pixels).

• A higher resolution means more pixels, which produces a sharper, more detailed image.
• A higher resolution also means a larger file size because there are more pixels to store.

Colour Depth

Colour depth is the number of bits used to represent the colour of each pixel.