Pixel Pictures
Computing · Year 3–Year 6
Shade the squares, and see the 1s and 0s the picture is stored as.
About the pixel pictures
An eight by eight grid to shade, and beside it the same picture written as 1s and 0s, one digit for every square. Each row of digits sits level with the row it came from, so a class can put a finger on the board and read across.
It is BLACK AND WHITE and nothing else, because that is what makes the code true: a square is on or it is off, a 1 or a 0. A palette would be a nicer drawing tool and a worse computing one.
The numbers are worked out from the squares rather than stored beside them, so the code and the picture can never disagree. Change one square and one digit changes.
Turn the numbers off for plain pixel art, which is worth having on its own: draw a letter, a space invader or a smiley, then turn them back on and ask how many bits it took.
Sixty-four squares is sixty-four bits, which is eight bytes. That is the sentence a Year 6 class is being led to.
How to use it on your whiteboard
- 1Tap a square to shade it, and tap it again to rub it out.
- 2Drag across the grid to shade a run of squares.
- 3Read a row of the picture and the row of digits beside it together.
- 4Ask the class to work out a row before you shade it.
- 5Turn the numbers off, draw a picture, then turn them on and read it back.
- 6Undo takes back the last square, and Clear starts again.
Questions
- Why only black and white?
- Because the lesson is that a picture is stored as numbers and there are only two of them. Three colours cannot be written as 1s and 0s, and the panel beside the grid would stop being true.
- Is this how images are really stored?
- It is how a black and white bitmap is stored, yes: one bit for every pixel, read row by row. A photograph adds colour, which is more numbers for each pixel, and compression, which is a different lesson.
- What is a bit?
- One 1 or one 0. This grid is sixty-four squares, so sixty-four bits, which is eight bytes.