  In this paper a new fractal image compression algorithm is proposed in which
the time of encoding process is considerably reduced. The algorithm exploits a
domain pool reduction approach, along with using innovative predefined values
for contrast scaling factor, S, instead of scanning the parameter space [0,1].
Within this approach only domain blocks with entropies greater than a threshold
are considered. As a novel point, it is assumed that in each step of the
encoding process, the domain block with small enough distance shall be found
only for the range blocks with low activity (equivalently low entropy). This
novel point is used to find reasonable estimations of S, and use them in the
encoding process as predefined values, mentioned above. The algorithm has been
examined for some well-known images. This result shows that our proposed
algorithm considerably reduces the encoding time producing images that are
approximately the same in quality.
