Lossy and Lossless Compression

• Compression


  Reducing file size while retaining the core information
• Compression means fewer bits are needed to represent the same information, reducing storage space and transfer times
• Two approaches to compression

  • Lossy
  • Lossless
• Lossy compression


  The algorithm physically removes data from the file, reducing file size but losing some data
• Lossy compression algorithms


  • JPEG for images
  • MP3 for audio
• Lossy compression


  Removes data that humans are least likely to recognize or notice
• Lossless compression


  Rearranges data to make it more efficient without deleting any data
• Run Length Encoding (RLE)


  Replace long runs of repeated data with frequency-data pairs
• RLE example with image data

  • 4 yellow
  • 1 blue
  • 4 purple
  • 1 blue
• RLE example with binary data

  • 5 zeros
  • 4 ones
  • 1 zero
• RLE works best with data likely to have lots of repeats, like images or matrices, but may not be effective for random or varied data