Bitmap graphics

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Key points

  • Bitmap graphics are stored as a grid of pixels. Each pixel is represented by a number that tells the computer what colour the pixel should be.
  • The bit depth of an image is the number of bits used to represent each pixel. A bit depth of 1 will only allow a 1 or 0 per pixel (black or white). A bit depth of 8 will allow 8 bits per pixel meaning the computer has 256 colours to choose from.
  • The colour for each pixel is often represented by a colour code, which uses a number of bits for red, green and blue. In HTML, this is represented as a 24 bit number, with 3 numbers between 0 and 255 for each colour.
  • The size of a bitmap graphic can be calculated by multiplying the resolution of the image by the bit depth. The bit depth can be worked out from the number of colours.

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