Topic 1g
Compression Methods
Learning Outcomes
By the end of this topic students should be able to:
- Define [Lossy | Lossless] compression.
- Explain the difference between Lossy/Lossless compression.
- Give an example of a Lossy Compression technique and explain how it works.
- Give an example of a Lossless Compression technique and explain how it works.
Learning Materials
- Readings
- Section 1.9 - pp 77-83
- Videos
- Code.org video about Compression featuring Aloe Blacc (you may not know his name, but you may recognize some of his music).
- Dr. Schafer explains the compression of text
- Note, there is a typo in my slide at about the 2:26 mark.
- The bit/ASCII encoding for a space is 00100000
- Five 0s after the 1
- I didn't notice that I only had seven of the eight bits there.
- Dr. Schafer explains the compression of pictures
- Activity
- Explore this tool for considering text compression from Code.org.
- Instructions
- Code.org compression simulator
- My dictionaries for the simulation activity. [Vaguely, an answer Key]
- Explore this tool for considering text compression from Code.org.
Checking for Understanding
- You are welcome to consider the Q&E problems on page 83. However, these do not align with our learning outcomes so do not use a failure as meaning you are in trouble.
- Give an example of a lossless compression technique (either specific or generic). Explain how it works and why it is a lossless technique.
- Give an example of a lossy compression technique (either specific or generic). Explain how it works and why we don't care that it is lossy.
Further Information
- This goes well beyond what you need to know about compression for this class, but this article/tool can help you explore and, maybe, better understand, how compression works for jpegs. Try out a few of their suggestions for changes to explore the system.