Goals and prerequisites

This lesson deals with issues related to lossless image compression. There is no special prerequisite for this lesson, so that it can be easily understood by almost everyone.

Image compression

Digital images are obtained by sampling and quantization of samples. Such simple image representation is related to significant redundancy of data. Within the data, there exists a lot of redundancy. Statistical redundancy is removed in the process of reversible or lossless compression. Irrelevancy of data is removed in the process of lossy or irreversible compression. Irrelevancy of data is related to information that is not significant for a viewer as it is difficult or even impossible to perceive.

A program or appliance that encodes row image data into a bitstream of compressed image data is called a coder (or encoder). A program or appliance that decodes a bitstream of compressed image data in order to get image samples ready to display is called a decoder.

Compression ratio and bpp (bit per pixel)