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Image Representation

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Image Representation

Images are everywhere on computers. Some are obvious, like photos on web pages and icons on buttons, but others are more subtle: a font is really a collection of images of characters, and a fax machines is really a computer that is good at scanning and printing.

This activity explores how images are displayed, based on the pixel as a building block. In particular, the great quantity of data in an image means that we need to use compression to be able to store and transmit it efficiently. The compression method used in this activity is based on the one used in fax machines, for black and white images.

Although the main activity is based on coloring a few dozen black pixels with a pencil, in live shows wen like to demonstrate it on a larger scale. One way to do this is to use a can of black spray paint and a square stencil to make a giant picture pixel-by-pixel. Another is to process a photograph of (say) a teacher to the kidfax code, and have a whole class decode the mystery photo.

  • Image Representation
Curriculum Links
Great Principles of Computer Science 
  • Recollection
ACM K12 Curriculum 
  • Level I (Grades K–2) Topic 11: Understand how 0s and 1s can be used to represent information, such as digital images and numbers.
New Zealand Curriculum 
  • Mathematics Level 1: Equations and expressions
  • Communicate and explain counting, grouping, and equal-sharing strategies, using words, numbers, and pictures.
  • Mathematics Level 2: Position and orientation
  • Create and use simple maps to show position and direction.
  • Technology Level 1:Technological systems
  • Understand that technological systems have inputs, controlled transformations, and outputs.
  • Technology Level 3: Technological systems
  • Understand that technological systems are represented by symbolic language tools and understand the role played by the “black box” in technological systems.
Videos 
Photos 
  • Mr. Idosaka explains the concept at Fujitsu Kids event with JOI, Japan

    Mr. Idosaka explains the concept at Fujitsu Kids event with JOI, Japan

  • Activity explained at Fujitsu Kids event with JOI, Japan

    Activity explained at Fujitsu Kids event with JOI, Japan

  • Image Representation

    Examples of worksheets from Susumu Kanmune

  • Kids' attempts at Fujitsu Kids event with JOI, Japan

    Kids' attempts at Fujitsu Kids event with JOI, Japan

Extension 

  • Computing Science Inside Workshop has an activity In the Picture which is a nice extension activity to this topic. In this workshop pupils consider image identification and explore methods that computers could use to achieve this. Using examples such as airport security and feature recognition it becomes clear why image identification systems are necessary. Pupils then try out one technique for image identification and the session finishes with a competition between teams to see who can correctly identify the most images. After this workshop pupils will appreciate the complexity of tasks such as automatic face recognition, and have some insight into how it could work.
    Note: You will need to apply and register in order to recieve the Workshop Pack for this activity.

  • Computing Science Inside Workshop has another activity Painting by Numbers which is a nice extension activity to this topic. In this workshop pupils look at the concept of image representation and question how computing devices such as digital cameras, phones, scanners and PCs can store and transmit images. The processes of digitisation, storage, transfer and rendering are explored using practical exercises, and there are plenty of options for further work following the workshop.
    Note: You will need to apply and register in order to recieve the Workshop Pack for this activity.

Other Resources 

  • An older version of this activity can be downloaded in PDF format here. The content is similar to the current version, but there's some extra technical information.

  • Wikipedia has useful articles on fax, run-length encoding and pixels

  • The Mathmaniacs website has a similar activity (lesson 3)

  • How Stuff Works: Fax Machine

  • Image Representation is demonstrated using Flash animation by Hiroki Manabe .

  • Brian Myers from the University of Cincinnati has a related activity in Image Processing and Computer Vision called Healthcare Imaging where students explore x-rays by comparing them to light rays, and then explore how to create 3D images using CT imaging. This activity was developed for high school students.

  • Wikipedia: Flatland : A Romance of Many Dimensions is an 1884 satirical novella by the English schoolmaster Edwin Abbott. Writing pseudonymously as "a square", Abbott used the fictional two-dimensional world of Flatland to offer pointed observations on the social hierarchy of Victorian culture. However, the novella's more enduring contribution is its examination of dimensions; in a foreword to one of the many publications of the novella, noted science writer Isaac Asimov described Flatland as "The best introduction one can find into the manner of perceiving dimensions." As such, the novella is still popular amongst mathematics, physics, and computer science students. For some exciting resources on the movie, please visit the following sites: