Data compression involves reducing file size by either discarding unnecessary data or by use of algorithms that look for repeating patterns in data (redundancy).

Visit the sites below then answer the following questions;

http://computer.howstuffworks.com/file-compression.htm/printable

http://computer.howstuffworks.com/question408.htm

1. Name two programs used for file compression.
   -Winzip
   -WinAce
   
   
2. What name is given to the file compression method that looks for redundant patterns?
   Lossless Data. This is when the original data is reconstructed to make it more easily compressed.
   Why can’t music be compressed efficiently with this type of  compression technique?
   Because music often don’t repeat as many text files as text files.
   
   
3. What method of compression is most suited to graphics and music files?
   Lossy compression. This is when data is compressed by getting rid of (losing) bits of data. This reduces the amount of data that needs to be held. It is most suited to graphics and music files as it eliminates bits of sound not heard by the humar ear in music files, and gets rid of pixels in an image.
   
   

 Use Gimp (Start > Programs > Gimp2) to open an image and then save it as a jpeg with different levels of compression. Paste these images below. Explain why the appearance of the images varies!!

Uncompressed (108.5)

 

Low Compression (9.37 KB)  

Medium Compression (4.82KB)

 High Compression (1.14KB)

The images appear different because each time the image is compressed bits of information (pixels) are taken out of the picture. At a low compression our brains fill in the gaps of the missing pixels, but as more pixels are removed, our brain finds it harder to fill in the missing pixels.