util.py 文件源码

def ellipse2bbox(a, b, angle, cx, cy):
        a, b = max(a, b), min(a, b)
        ca = sp.cos(angle)
        sa = sp.sin(angle)
        if sa == 0.0:
            cta = 2.0 / sp.pi
        else:
            cta = ca / sa

        if ca == 0.0:
            ta = sp.pi / 2.0
        else:
            ta = sa / ca

        x = lambda t: cx + a * sp.cos(t) * ca - b * sp.sin(t) * sa


        y = lambda t: cy + b * sp.sin(t) * ca + a * sp.cos(t) * sa

        # x = cx + a * cos(t) * cos(angle) - b * sin(t) * sin(angle)
        # tan(t) = -b * tan(angle) / a
        tx1 = sp.arctan(-b * ta / a)
        tx2 = tx1 - sp.pi
        x1, y1 = x(tx1), y(tx1)
        x2, y2 = x(tx2), y(tx2)

        # y = cy + b * sin(t) * cos(angle) + a * cos(t) * sin(angle)
        # tan(t) = b * cot(angle) / a
        ty1 = sp.arctan(b * cta / a)
        ty2 = ty1 - sp.pi
        x3, y3 = x(ty1), y(ty1)
        x4, y4 = x(ty2), y(ty2)

        minx, maxx = Util.minmax([x1, x2, x3, x4])
        miny, maxy = Util.minmax([y1, y2, y3, y4])
        return sp.floor(minx), sp.floor(miny), sp.ceil(maxx), sp.ceil(maxy)