// The x,y increments from an endpoint needed to create a rectangle...
double ddx = -scale * (double)dY;
double ddy = scale * (double)dX;
ddx += (ddx > 0) ? 0.5 : -0.5;
ddy += (ddy > 0) ? 0.5 : -0.5;
int dx = (int)ddx;
int dy = (int)ddy;

// Now we can compute the corner points...
int xPoints[] = new int[4];
int yPoints[] = new int[4];

xPoints[0] = x1 + dx; yPoints[0] = y1 + dy;
xPoints[1] = x1 - dx; yPoints[1] = y1 - dy;
xPoints[2] = x2 - dx; yPoints[2] = y2 - dy;
xPoints[3] = x2 + dx; yPoints[3] = y2 + dy;