How digital images are made — Computing, 7–10 years
See how a picture on a screen is built from a grid of tiny coloured squares called pixels.
A picture is a grid
Zoom in far enough on a digital picture and you can see tiny squares called pixels. Each pixel has a colour, and the complete grid makes your eyes see a picture. More pixels can show finer detail, while fewer pixels make the squares easier to notice.
Why use pixels?
A computer needs a precise, countable way to store a picture and change it on a screen. A grid gives every small place an address and a colour, instead of asking the computer to remember a whole scene at once. This also makes copying and editing possible.
Making a tiny picture
Use a 3 by 3 grid and colour every square white. Change the centre square to black: you now have a tiny black dot. Change the four corner squares to black too, and the grid stores five black pixels and four white pixels as a simple pattern.
It is not made of ink
A common mistake is imagining that a digital photo contains a tiny coloured object for every part of the real scene. That seems reasonable because the picture looks continuous. In fact, the screen shows many separate pixels so close together that your eyes blend them.
Screens and cameras
Pixels appear in phone photos, television pictures, computer games and digital maps. Zooming into a map can reveal the pixels, while a high-resolution camera captures enough of them to keep faces and leaves looking smooth. Printing turns the stored pattern into marks on paper.
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