That Blue Square Thing

Syllabus content:
PDF iconUnit 3 image content – just image encoding
Note: this syllabus content is a slightly amended version of the one published freely on the web by AQA. I have made very minor adjustments to remove some content less suitable for students to use and it is presented here simply to allow the children I teach to download a usable copy of the syllabus content. It is copyright AQA and reproduced here simply to make access easier for students. No attempt to claim copyright is being made, although I could have copied the text into my own interpretation...

AQA Computer Science GCSE

This page is up to date for the AQA 8525 syllabus for exams from 2022.

Data Representation – Representing Images

All data that is used by computers has to be represented using binary numbers. Everything. Including images.

The way in which computers break down images into a grid of pixels and then apply a value to each pixel is actually fairly simple once you get your head around it.

PDF iconImage Representation Slides – slides from class

PDF iconImage Representation sheet – textbook style double page spread

PDF iconImage file definitions – single slide

All the key information is in those documents, but you also need to be able to do calculations, which is the trickier bit.

PDF iconImage File Calculations slides – simple calculations...

PDF iconImage File Size summary – a single slide that summarises the file size workings formulae

There is a really annoying question the exam board asks regularly that frequently catches people out:

PDF iconMore complex image file size calculations – this is tricky to get your head around. Just trust it

Some other resources:

PDF iconBlack and white bitmap – for printing by me and cutting up

PDF iconImage Exam Questions – some quite complex questions here which show what could be done and how this topic relates back to binary and hexadecimal. Your real questions are actually likely to be easier than these...