Year 9
Lesson 2 A splash of colour
In the early days of personal computers, graphics were displayed in a range of different resolutions and colour depths, depending on the hardware available. Nowadays, while resolution is still being increased, there is no mention of colour depth or the number of possible colours available. We have used 24 or 32 bits for years, as this has been sufficient. In the previous lesson, learners were introduced to the idea that the colour of each pixel can be represented as a sequence of binary digits. In this lesson, they will explore the most common representation of colour as a mixture of red, green, and blue: the level of each of these colours in the mixture is represented using an 8-bit sequence, producing a total of 24 bits to represent the colour of any single pixel. Learners will also build on their existing knowledge to calculate the representation size of digital images.
Learning objectives
- Describe how colour can be represented as a mixture of red, green, and blue, with a sequence of bits representing each colour’s intensity
- Compute the representation size of a digital image, by multiplying resolution (number of pixels) with colour depth (number of bits used to represent the colour of individual pixels)
- Describe the trade-off between representation size and perceived quality for digital images
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