Chapter 17
Image Compression and Coding
What will we learn?
- What is the meaning of compressing an image?
- Which types of redundancy can be exploited when compressing images and how is this usually done?
- What are the main (lossy and lossless) image compression techniques in use today?
- How can we evaluate the (subjective) quality of an image that has undergone some type of processing (e.g., lossy compression) in an objective way?
- What are the most popular contemporary image compression standards?
17.1 Introduction
Images can be represented in digital format in many different ways, the simplest of which consists in simply storing all the pixel values in a file following a certain convention (e.g., row first, starting from the top left corner). The result of using such raw image representations is the need for large amounts of storage space (and proportionally long transmission times in the case of file uploads/downloads). The need to save storage space and shorten transmission time and the human visual system tolerance to a modest amount of loss have been the driving factors behind image compression techniques.
Image compression techniques are behind the most popular image and video applications and devices in use today, such as DVD players, digital cameras, and web-based video streaming. Contemporary image compression algorithms are capable of encoding images with high compression efficiency and minimal noticeable degradation of visual quality.
Compression methods can be lossy ...
