Calculates the number of required iterations to determine the divergence
of the sequence of points obtained by the recursion
zn + 1 = (zn)2 + c
where c is the point passed to the setDefiningPoint method and is
constant during the calculation of the fractal and z1 is a
point determined by screen coordinates.
Calculates the number of required iterations to determine the divergence
of the sequence of points obtained by the recursion
z1 := 1, zn + 1 = (zn)2 + c
where c is the result of the conversion of the specified pixel to a
complex number.
Returns the number of required iterations to determine divergence of a
certain sequence at the specified pixel converted to a complex number as
it is stored in one of the buffers used by this
ThreadedDoublePrecisionFractalGenerator.