Image Representation

This lesson covers how computers represent digital images, including bitmaps, pixels, resolution, colour depth, file size calculations, and the difference between bitmap and vector graphics. This is required for the OCR H446 specification.

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Bitmap Images

A bitmap (raster) image is made up of a grid of tiny coloured squares called pixels (picture elements). Each pixel has a single colour, and when viewed together, the pixels form a complete image.

Key Properties

Property	Definition
Pixel	The smallest individual element of a bitmap image
Resolution	The number of pixels in the image (width x height)
Colour depth	The number of bits used to represent the colour of each pixel
Metadata	Information stored alongside the image data (e.g., resolution, colour depth, file format)

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Resolution

Resolution refers to the number of pixels per unit area, often measured in pixels per inch (PPI) or dots per inch (DPI), or simply as total pixel dimensions (e.g., 1920 x 1080).