孤单星球
跳动旋律
贝塞尔曲线画圆控制点的计算
/// 控制点的计算, 可以以此画圆 θ 为圆N等分的角度， 不要大于90度
/// (x0,y0),(x3, y3)为起点和终点, (x,y)为圆心
/// 贝塞尔曲线画圆，若分成n等分，则曲线端点到最近控制点的最佳距离为(4/3)*((1-cos(θ/2))/sin(θ/2))*r , θ = 2π/n;
/// x1 = x0 - (4/3)*((1-cos(θ/2))/sin(θ/2))*(y0-y); (x ,y)为圆心
/// y1 =y0 + (4/3)*((1-cos(θ/2))/sin(θ/2))*(x0-x)
/// x2 =x3 + (4/3)*((1-cos(θ/2))/sin(θ/2))*(y3-y)
/// y2= y3 - (4/3)*((1-cos(θ/2))/sin(θ/2))*(x3-x)
static getCubicControlPoint(
{@required x0,
@required y0,
@required x3,
@required y3,
@required radians,
@required x,
@required y}) {
double h = 4 / 3 * math.tan(radians / 4);
double x1 = x0 - (h * (y0 - y));
double y1 = y0 + h * (x0 - x);
double x2 = x3 + h * (y3 - y);
double y2 = y3 - (h * (x3 - x));
return {
'x1': x1,
'x2': x2,
'y1': y1,
'y2': y2,
};
}
实现的效果还是和预期效果有差异，如何取圆上的一点，利用贝塞尔曲线画圆，求贝塞尔控制点等
