Digital images and pixels
Understand how digital images are built from pixels and be able to describe a simple image using numbers.
Prerequisites
- AInput and outputrequired
Everyday explanation
Open an image in a viewer and zoom in significantly. The image becomes blocky. Each small square has a single colour. These squares are called pixels.
An image of a product or a face is just thousands of pixels with different colours. The computer does not see the object — it sees a list of values: «square 1 is dark, square 2 is dark, square 3 is light …».
More pixels result in a sharper image. Fewer pixels make the image look like a grid.
Interactive
Describe with numbers. Take an 8 × 8 grid. Write 1 in squares that should be black and 0 in squares that should be white. Draw a simple symbol, such as a letter or a logo.
Read the rows to a colleague: «0 1 1 0 1 1 0 0 …». Can the colleague draw the same image without seeing yours? If so, you have sent an image as numbers — exactly as computers do.
0 1 1 0 0 1 1 0
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
0 1 1 1 1 1 1 0
0 0 1 1 1 1 0 0
0 0 0 1 1 0 0 0
Mastery means
- Explains that an image on a screen consists of small coloured squares (pixels)
- Can draw a simple figure on a grid and describe it using numbers
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Sources
- CS Unplugged (CC BY-SA 4.0) — CC BY-SA 4.0
- Wikipedia — Pixel (CC BY-SA 4.0) — CC BY-SA 4.0