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compface, uncompface - compress and expand 48x48x1 face image files
compface (buf)
uncompface (buf)
char *buf
compface
is a function for generating highly compressed representations of 48x48x1
face image files. uncompface is an inverse function which performs an inverse
transformation with no loss of data. The algorithm used is highly tuned
for its purpose and achieves better than a five to one compression ratio
on average. In both functions, input is via a NULL terminated string and
a NULL terminated output string is written over the input string. Buf should
therefore point to a block of 2K size or more to avoid buffer overruns
during output generation.
The input format for compface (and the output
format for uncompface) is 48 lines each of 3 sixteen bit hexadecimal integers,
comma terminated in C initialiser style. The output format of compface (and
the input format for uncompface) is some number of lines made up of a space
followed by printable characters (in the range ‘‘!’’ to ‘‘~’’ inclusive). The first
line contains 72 characters and following lines contain 79 characters except
that the last line may be short.
The amount of compression obtained varies
between face image files but the output of compface averages less than
200 characters. The average number of output lines is three.
The
return value is normally 0. 1 will be returned if extra input has been ignored
during a compress operation. -1 is returned in the case of an invalid input
format. -2 is returned if an internal buffer overrun occurs.
Compface(1)
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