This workshop investigates how images are stored as data, and shows the difference that ‘bit depth’ makes to the quality of images and number of colours.
It begins by looking at paintings and how, using only paint, images were difficult to edit – however digital images are much easier. Pupils with access to photo editing software such as GIMP (free, open-source software) can make simple adjustments to found images, although this is not critical to the lesson.
Learners are then asked to use conditional cell formatting in a spreadsheet application to create simple graphics. They learn that, by increasing the amount of data in each cell and changing the formatting rules accordingly, an increased number of colours can be used in the image. The correlation between bit depth, colour range and overall file size is made clear.
Finally, the effect of image compression is examined, and students take a brief look at vector images and how they are stored.
The resource is planned as an extended enrichment or collapsed-timetable activity, but could easily be adapted for teaching over a series of lessons.
Digital School House is associated and fully supported by Ukie