int im_fractsurf(in, frdim, size) IMAGE *in; double frdim; int size;
creates a fracta surface. The program initially creates a gaussian
noise image (im_gausnoise(3)) of sizes size x size. The image is then
filtered (im_flt_image_freq(3)) in order to force the power spectrum to
decay according to the desired fractal dimension frdim. The result is
a one band float image and should be scaled for display.
The function returns 0 on success and -1 on error.