int poly_p_center(gpc_polygon *p, double *cx, double *cy){
double *x, *y, *a, A=0.0, X=0.0, Y=0.0;
int i;
size_t s;
s = sizeof(double)*p->num_contours;
a = (double *)alloca(s);
x = (double *)alloca(s);
y = (double *)alloca(s);
for (i=0; i < p->num_contours; i++) {
a[i] = ((p->hole[i]) ? -1.0 : 1.0) * poly_c_area(p->contour+i);
if (poly_c_center(p->contour+i, x+i, y+i) != 0)
return 1;
}
for (i=0; i < p->num_contours; i++)
A += a[i];
for (i=0; i < p->num_contours; i++) {
X += a[i] * x[i];
Y += a[i] * y[i];
}
if (A == 0)
return 1;
*cx = X / A;
*cy = Y / A;
return 0;
}
static PyObject *Polygon_center(Polygon *self, PyObject *args) {
int i=INDEF;
double cx, cy;
if (! PyArg_ParseTuple(args, "|i", &i))
return Polygon_Raise(ERR_ARG);
if (i!=INDEF) {
if ((i >= 0) && (i < self->p->num_contours)) {
if (poly_c_center(self->p->contour+i, &cx, &cy) !=0)
return Polygon_Raise(ERR_INV);
} else
return Polygon_Raise(ERR_IND);
} else {
if (poly_p_center(self->p, &cx, &cy) != 0)
return Polygon_Raise(ERR_INV);
}
return Py_BuildValue("dd", cx, cy);
}
