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Test

16 - Run Length Encoding

Run Length Encoding

One of the simplest examples of compression is RLE. RLE is a basic form of data compression that converts consecutive identical values into a code consisting of the character and the number marking the length of the run. The more similar values there are, the more values can be compressed. The sequence of data is stored as a single value and count.

For example, consider a screen containing plain black text on a solid white background. There will be many long runs of white pixels in the blank space, and many short runs of black pixels within the text. A hypothetical scan line, with B representing a black pixel and W representing white, might read as follows:

WWWWWWWWWWWWBWWWWWWWWWWWWBBBWWWWWWWWWWWWWWWWWWWWWWWWBWWWWWWWWWWWWWW

With a run-length encoding (RLE) data compression algorithm applied to the above hypothetical scan line, it can be rendered as follows:

12W1B12W3B24W1B14W

This can be interpreted as a sequence of twelve Ws, one B, twelve Ws, three Bs, etc.

Additional Reading

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