CS Unplugged, Georges Seurat, Pixels, RGB and my year 1 class

On Wednesday 28 October I had a pretty interesting year 1 lesson. This term the girls are doing light and sound in their science unit, so to link in ICT I thought I would teach the girls about how a computer stores and displays images, and display light. In the first lesson of the term I used a CS Unplugged lesson called Image Representation. It teaches students about why we use computers to store images and how computers display images using pixels as building blocks. There is an activity where students construct black and white images on a grid of pixels using some basic coordinates. It represents how a computer builds (displays) a stored image using a set of numbers, which represent the colour and location of the pixel.

Pixel art
Pixel art

The girls did really well and all of them managed to construct at least 1 or 2 pixel images. One girl managed to complete all 3, fast learner indeed.

Image representation
Image representation

In the second lesson I took this concept a step further. I taught the girls that TVs and computer screens use the RGB color model to display light, and that this is an ‘additive’ model where colours can be combined to create other colours. I said that over 100 years ago a French painter called Georges Seurat (1859 – 1891) painted using a very distinctive technique called ‘Pointillism’. I showed them this picture (The Seine and la Grande Jatte – Springtime) from 1888 and told them to look very closely at it and asked them what they noticed about it.

The Seine and la Grande Jatte - Georges Seurat (1888)
The Seine and la Grande Jatte – Georges Seurat (1888)

They said that the painting was made from ‘pixels’, exactly what I wanted them to notice. Seurat’s distinctive style of using small dot like strokes of colour that seemed to blend from a distance. We then looked at how we can create pixel images using multiple colours. By numbering the chosen colours and stating the length of each run of pixels in a line. The girls used a 16×16 (254 pixels) grid and a selection of colours to draw there own colourful ‘Seurat’ style image. They then had to write down the number of the length of pixels and the number of the colour of the pixel in a blank grid below their image. When they had finished writing the instructions they will give the numbers to a friend so they can recreate the image exactly from just the numbers, computer science unplugged.

Next time:

  • Make the lesson more relevant to the young girls by using images more suitable for the age
  • Give them a mystery image to draw from just the numbers first
  • Look at how much storage is needed by a computer to store a single image
  • Look at a camera in the classroom or on the iPad, find out how many pixels the camera takes in a shot, it will be alot
  • Try to understand that the less pixels an image has the more ‘blocky’ it will appear, the more pixels an image has the clearer and sharper the image will appear
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