This makes the selection between the two.
It takes two arguements and three optional ones.
The first arguement is the image.
The second is the max difference when the size of
the picture is used to devide each other.
The third is continuation of the second, but defaults
what ever the second is if it is not specified.
The fourth is comparative X resolution to use.
The fifth is the comparative Y resolution to use.
Upon a error, it returns undef.
my $filltype=$iffs->select($image, .2, undef, 800, 600);