LOSSY VS LOSSLESS 

Compression exists to reduce the size of the file. The impact of this is that:

• less bandwidth required 
• less storage space required
• shorter transmission time
  

Lossy removes data permanently – small file size but worse quality

Lossless removes data temporarily

Lossy

Lossy Is a compression method that uses an algorithm to scan the image or file and determines which pieces of data are the same. It will then remove these permanently for each file. For this reason, the file size is reduced and the quality also decreases. For example, reducing resolution or colour depth, reducing sample rate or resolution

• Permanently removes some data
• Recreates the file using the remaining data and uses algorithms to guess the removed content
• Uncompressed data is not the same as the original

Lossless

Lossless is a compression method that uses an algorithm called RLE (Run Length Encoding). The algorithm counts the number of pixels or data that occurs and keeps it as a run count. Run value is the data that needs to be represented. 

• Finds groups of repeating data and records the data only once along with the number of times it was repeated
• When data is uncompressed it is restored exactly as it was in the original
• Don’t add the same values after the frame has already passed.

Metadata

• Metadata is data about data
• It is information other than image data that is stored in a file

This will include:

• Color depth in bits per pixel
• Resolution (Height and width in pixels)
• Date created
• Author