float * localbuf
temporary buffer for horiz_slice. NULL if not used
void(* verti_slice)(float *buffer, int width, int height, int slice_start, int slice_end, int steps, float nu, float bscale)
void(* horiz_slice)(float *buffer, int width, int height, int steps, float nu, float bscale, float *localbuf)
void(* postscale_slice)(float *buffer, int length, float postscale, float min, float max)