| 2.1
Run Length
Encoding (RLE)
Run-length Encoding, or RLE is a
technique used to reduce the size of a repeating string of
characters. This repeating string is called a run, typically
RLE encodes a run of symbols into two bytes , a count and
a symbol. RLE can compress any type of data regardless of its information
content, but the content of data to be compressed affects the
compression ratio. RLE cannot acheive high compression ratios compared
to other compression methods, but it is easy to implement and is quick to
execute. Run-length encoding is supported by most bitmap file formats such
as TIFF, BMP and PCX.
Compression
is normally measured with the compression ratio :
| Compression Ratio =
original size / compressed size : 1
|
Consider a character run of 15 'A' characters
which normally would require 15 bytes to store :
With RLE, this would only require
two bytes to store, the count (15) is stored as the first byte and the
symbol (A) as the second byte.
continue.......
|