IOS CALayer的阴影属性

@property(nullable) CGColorRef shadowColor;

/* The opacity of the shadow. Defaults to 0. Specifying a value outside the
 * [0,1] range will give undefined results. Animatable. */

@property float shadowOpacity;

/* The shadow offset. Defaults to (0, -3). Animatable. */

@property CGSize shadowOffset;

/* The blur radius used to create the shadow. Defaults to 3. Animatable. */

@property CGFloat shadowRadius;

/* When non-null this path defines the outline used to construct the
 * layer's shadow instead of using the layer's composited alpha
 * channel. The path is rendered using the non-zero winding rule.
 * Specifying the path explicitly using this property will usually
 * improve rendering performance, as will sharing the same path
 * reference across multiple layers. Upon assignment the path is copied.
 * Defaults to null. Animatable. */

@property(nullable) CGPathRef shadowPath;

1、shadowColor：阴影颜色

2、shadowOpacity：不透明度，取值范围[0,1],可以对应UIView的 透明度 进行理解
3、shadowRadius：对阴影的模糊度，默认值为3 ，值越大，越模糊，越自然如果为零则有明确的边界线

4、shadowOffset：阴影的偏移量，默认（0，-3）

5、shadowPath：可以指定阴影的形状，可以矩形，圆形甚至是贝塞尔曲线生成的任意形状，如下代码，生成的就是矩形的阴影

CGFloat x,y,w,h;
CGMutablePathRef squarePath = CGPathCreateMutable();
CGPathAddRect(squarePath, NULL, CGRectMake(x, y, w, h));
view.layer.shadowPath = squarePath;

相同