Compression Losses

We have two types of Compression Losses.

Lossless Compression:

• This compression enables the restoration of a file to its original state, without losing a single bit of data, when the file is uncompressed.
• This are important in text file compression because if loss of any words or numbers it change the original content.
• Formats such as GIF, PNG, BMP are use lossless compression.

Example:

• An example of seven gray pixels:
• 128, 127, 126, 121, 124, 123, 120
• Can be re-written in shorter numbers requiring less bits like:
• 128, -1, -1, -5, +3, -1, -3

Lossy Compression:

• This compression reduces the size of a file by eliminating bits of information.
• It permanently deletes the unnecessary data.
• This is useful with images, audio, graphics. Where if we loss a some bits it is not much effect that means  a loss of quality is affordable.
• Formats like JPEG are use lossy compression.

Example:

• The previous sequence of numbers:
• 128, 127, 126, 121, 124, 123, 120  
• can be re-written like:
• 128 - 6
• Result after decompression:
• 128, 127, 126, 125, 124, 123, 122

Example of Compression: