view的阴影属性主要有5个
//shadowColor //阴影颜色
//shadowOpacity //阴影不透明度
//shadowRadius //阴影半径
//shadowOffset //阴影偏移量
//shadowPath //阴影路径
//前四个属性的效果
UIView * view = [[UIView alloc] initWithFrame:CGRectMake(30, 100, self.view.bounds.size.width-60, 200)];
view.backgroundColor = [UIColor whiteColor];
view.layer.shadowColor = [UIColor redColor].CGColor;
view.layer.shadowOpacity = 1; //阴影不透明度 【0-1】 0->完全透明 1->完全不透明 越大越明显 默认0
view.layer.shadowRadius = 20; //阴影半径 默认3
view.layer.shadowOffset = CGSizeMake(0, 0); //阴影偏移量 （右，下） 默认（0，-3）
[self.view addSubview:view];
效果图
添加以下代码设置贝塞尔曲线
//view.layer.shadowPath 贝塞尔曲线
UIBezierPath *path = [UIBezierPath bezierPath];
float width = view.bounds.size.width;
float height = view.bounds.size.height;
float x = view.bounds.origin.x;
float y = view.bounds.origin.y;
float addWH = 40;
CGPoint topLeft = view.bounds.origin; //左上角
CGPoint topMiddle = CGPointMake(x+(width/2),y-addWH); //中上点
CGPoint topRight = CGPointMake(x+width,y); //右上角
CGPoint rightMiddle = CGPointMake(x+width+addWH,y+(height/2)); //右中点
CGPoint bottomRight = CGPointMake(x+width,y+height); //右下角
CGPoint bottomMiddle = CGPointMake(x+(width/2),y+height+addWH); //中下点
CGPoint bottomLeft = CGPointMake(x,y+height); //左下角
CGPoint leftMiddle = CGPointMake(x-addWH,y+(height/2)); //左中点
[path moveToPoint:topLeft];
//添加四个二元曲线
//左上角到右上角，中上为控制点
[path addQuadCurveToPoint:topRight
controlPoint:topMiddle];
//右上角到右下角，右中为控制点
[path addQuadCurveToPoint:bottomRight
controlPoint:rightMiddle];
//右下角到左下角，中下为控制点
[path addQuadCurveToPoint:bottomLeft
controlPoint:bottomMiddle];
//左下角到左上角，左中为控制点
[path addQuadCurveToPoint:topLeft
controlPoint:leftMiddle];
//设置阴影路径
view.layer.shadowPath = path.CGPath;
[self.view addSubview:view];
效果图
