Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats


Run Length Encoding

General Principle

Control Characters

RLE for Image Data

Pixel Coding

Sequential Processing

Line Coding

Cross-Coding

End of Line Marker

Repetition of Lines

Lossy RLE

Implementations


Glossary

Index


Download


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Sequential Processing


A general purpose encoder processes data sequentially in a one-dimensional structure. Procedures especially designed for image data could additionally benefit from their two-dimensional characteristic. The diagrams below shall demonstrate some possible strategies:


horizontal processing vertical processing

tiled processing diagonal processing (zig-zag-scanning)


In practice this processes are not very important for native image data, but equivalent technologies are commonly in use. The final entropy coding according to JPEG uses RLE to encode the quantified AC coefficients. Therefore a diagonal zig-zag-processing is applied. This coefficients do not represent pixels, but frequencies describing the particular area.


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RLE for Image Data Pixel Coding Line Coding