UIView設置陰影CALayer的屬性:

shadowColor，

shadowOffset，

shadowOpacity，

shadowRadius,

shadowPath

 加陰影
//shadowColor陰影顏色
_imageView.layer.shadowColor = [UIColor blackColor].CGColor;
/**
shadowOffset陰影偏移,x向右偏移4，y向下偏移4，默認(0, -3),這個跟shadowRadius配合使用
*/
_imageView.layer.shadowOffset = CGSizeMake(4,4);
//陰影透明度，默認0
  _imageView.layer.shadowOpacity = 0.8;
//陰影半徑，默認3
 _imageView.layer.shadowRadius = 4;  

   //shadowColor陰影顏色
 _imageView1.layer.shadowColor = [UIColor yellowColor].CGColor;
   shadowOffset陰影偏移，默認(0, -3),這個跟shadowRadius配合使用
  //陰影透明度，默認0
  _imageView1.layer.shadowOffset = CGSizeMake(0,0);
  _imageView1.layer.shadowOpacity = 1;
  // 陰影半徑，默認3
 _imageView1.layer.shadowRadius = 3;

//路徑陰影
  UIBezierPath *path = [UIBezierPath bezierPath];  
  float width = _imageView1.bounds.size.width;
  float height = _imageView1.bounds.size.height;
  float  x = _imageView1.bounds.origin.x;
  float  y = _imageView1.bounds.origin.y;
  float addWH = 10;
  CGPoint topLeft = _imageView1.bounds.origin;  
  CGPoint topMiddle = CGPointMake(x+(width/2),y-addWH);  
  CGPoint topRight = CGPointMake(x+width,y);  
  CGPoint rightMiddle = CGPointMake(x+width+addWH,y+(height/2));  
  CGPoint bottomRight = CGPointMake(x+width,y+height);  
  CGPoint bottomMiddle = CGPointMake(x+(width/2),y+height+addWH);  
  CGPoint bottomLeft = CGPointMake(x,y+height);  
  CGPoint leftMiddle = CGPointMake(x-addWH,y+(height/2)); 
  [path moveToPoint:topLeft];                   
  //添加四個二元曲線
  [path addQuadCurveToPoint:topRight controlPoint:topMiddle];  
  [path addQuadCurveToPoint:bottomRight controlPoint:rightMiddle];     
  [path addQuadCurveToPoint:bottomLeft controlPoint:bottomMiddle];      
  [path addQuadCurveToPoint:topLeft controlPoint:leftMiddle];  
  //設置陰影路徑
 _imageView1.layer.shadowPath = path.CGPath;