Home Plan and prepare Scope and Sequence (F-10) 5-6 Representing images using binary

Unit Representing images using binary

Year level: 5-6 Topic: Data representations Time: 4 hours

Digital images are encoded in binary. Students learn about pixels and the way computers store an image as an array of individual pixels, each of which has a particular colour. Students make connections between the amount of data used by the computer to store, transmit and create an image and the file size of different images (generally, the more pixels and more bits to encode the image, the larger the file size).

Topic Overview
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Topic Unit Map
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Unit Overview
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Unit SOLO Taxonomy
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Flow of Activities

Activity Coding instructions

How can you use code to represent instructions?

Australian Curriculum Alignment

What's this about?

A grid is a simple way of representing picture elements (pixels). Each square can represent a pixel. Creating instructions to shade a grid gives students an understanding of the ways to represent the square: shaded or not shaded (on/off). On/off state is the basis of the binary system.

Learning tasks

  1. Introduce the task of shading a grid made up of squares, for example 5 x 5. One student shades the square then comes up with their own code to explain to a partner how to replicate the pattern of shaded squares.
  2. Students choose from a variety of ways to encode their pattern. There are many ways to represent the command of shading a square: a letter B for black, a scribble, a pen icon, a plus sign, a number.

Supporting Resources

Introducing algorithms Use the ‘Dare to square’ task of the lesson idea. Students encode and decode the shading of a grid. Adapt this activity to focus on ways to represent the command to code the square being shaded.

Assessment

Achievement Standard

Explain how digital systems use whole numbers as a basis for representing a variety of data types.

Suggested approaches may include

  • Research plan
  • Checklist (digital literacy skills)

Activity Coding an image using binary

How can I encode a black and white image using binary?

Australian Curriculum Alignment

What's this about?

Students create an image made up of only black and white squares. This task introduces them to how binary numbers are used to represent images.

0 represents black and 1 represents white. One binary digit is a bit. This is an example of colouring 1 bit per pixel; it is either black or white.

There is a direct relationship between the width and height of the image and the number of pixels and image detail.

Learning tasks

  1. Provide students with the task of creating an image based on either a black or white pixel.
  2. If doing this as an unplugged activity students work in pairs to encode their own image using 0s and 1s and swap with their partner to decode and then compare to the original image.
  3. Alternatively, use relevant online tools such as Code.org’s pixilation tutorial.

Supporting Resources

Using binary to create on/off pictures This lesson idea introduces students to representing images using 0 and 1. Black and white pixilation tutorial Explore creating black and white images using Code.org.

Assessment

Achievement Standard

Explain how digital systems use whole numbers as a basis for representing a variety of data types.

Suggested approaches may include

  • Artefact analysis: Represent an image using 1 bit/pixel (0 or 1)
  • Explain using Think Aloud

Activity Coding a colour image

How can I encode a colour image using binary?

Australian Curriculum Alignment

What's this about?

On a computer screen a colour image is made by mixing red, green and blue (RGB) light. This mix of light can be represented in binary in three digits. For example, (0,0,0) is no red, no green and no blue (making black). White is represented as (1,1,1). This is an example of RGB colouring 3 bits per pixel and results in 8 colours.

Learning tasks

  1. Students interested in finding out how to create colours using binary numbers can progress through the Code.org pixilation tutorial, and the colour tutorial.
  2. Challenge students to create a colour image using up to 8 colours. Explore changing the width and length of the image and the relationship between image detail (quality) and the number of pixels.

Supporting Resources

Using binary to create on/off pictures Use the learning demo part of the lesson to explore how to create a colour image using RGB, represented in binary as 3 bits. Colour pixilation tutorial Explore creating pixel images using this Code.org tutorial.

Assessment

Achievement Standard

Explore creating pixel images using this Code.org tutorial.

Suggested approaches may include

  • Artefact analysis: Represent an image using 3 bits/pixel (RGB)
  • Explain using Think Aloud

Assessment Resources

Pixels and binary digits Students are given a bitmap image made up of coloured pixels. They explain how the image is made up of binary digits that represent each pixel. Students represent 8 colours using binary digits. Teachers assess the student’s demonstrated knowledge/skills using the checklist provided.

Activity Create an image using binary

How can I design my own pixel image?

Australian Curriculum Alignment

What's this about?

Students apply their understanding about how binary is used to create an image. They create their own image for a particular purpose by encoding a grid of pixels.

Learning tasks

  1. Set a task of creating a pixel image for a particular purpose; for example, create a character to import into a visual programming software such as Scratch; an avatar to use in safe online environments; a card for a celebration; or a symbol to convey a message to be displayed around the school. Collectively establish the criteria and evaluate the solutions.

Supporting Resources

Colour pixilation tutorial Explore creating pixel images using this Code.org tutorial. How to do pixel art with MS Windows 7 Paint View a YouTube tutorial showing how to use a paint program to create an image.

Assessment

Achievement Standard

Explain how digital systems use whole numbers as a basis for representing a variety of data types.

Suggested approaches may include

  • Rubric: Scope for a range of abilities, skills and understanding (creativity), based on solo taxonomy (above)
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