绘制view 中间镂空 周围半透明

• (instancetype)initWithFrame:(CGRect)frame
  {
  self = [super initWithFrame:frame];
  if (self) {
  //设置 背景为clear
  self.backgroundColor = [UIColor clearColor];
  self.opaque = NO;
  }
  return self;
  }

• (void)drawRect:(CGRect)rect {

  [[UIColor colorWithWhite:0 alpha:0.5] setFill];
  //半透明区域
  UIRectFill(rect);

  //透明的区域
  CGRect holeRection = CGRectMake(100, 200, 200, 200);
  /** union: 并集
  CGRect CGRectUnion(CGRect r1, CGRect r2)
  返回并集部分rect
  */

  /** Intersection: 交集
  CGRect CGRectIntersection(CGRect r1, CGRect r2)
  返回交集部分rect
  */
  CGRect holeiInterSection = CGRectIntersection(holeRection, rect);
  [[UIColor clearColor] setFill];

  //CGContextClearRect(ctx, <#CGRect rect#>)
  //绘制
  //CGContextDrawPath(ctx, kCGPathFillStroke);
  UIRectFill(holeiInterSection);

}

• (void)drawRect:(CGRect)rect {
  //中间镂空的矩形框
  CGRect myRect =CGRectMake(100,100,200, 200);

  //背景
  UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:0];
  //镂空
  UIBezierPath *circlePath = [UIBezierPath bezierPathWithOvalInRect:myRect];
  [path appendPath:circlePath];
  [path setUsesEvenOddFillRule:YES];

  CAShapeLayer *fillLayer = [CAShapeLayer layer];
  fillLayer.path = path.CGPath;
  fillLayer.fillRule = kCAFillRuleEvenOdd;
  fillLayer.fillColor = [UIColor whiteColor].CGColor;
  fillLayer.opacity = 0.5;
  [self.layer addSublayer:fillLayer];

}

• (void)addArc {
  //中间镂空的矩形框
  CGRect myRect =CGRectMake(100,100,200, 200);

  //背景
  UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:[UIScreen mainScreen].bounds cornerRadius:0];
  //镂空
  UIBezierPath *circlePath = [UIBezierPath bezierPathWithOvalInRect:myRect];
  [path appendPath:circlePath];
  [path setUsesEvenOddFillRule:YES];

  CAShapeLayer *fillLayer = [CAShapeLayer layer];
  fillLayer.path = path.CGPath;
  fillLayer.fillRule = kCAFillRuleEvenOdd;
  fillLayer.fillColor = [UIColor whiteColor].CGColor;
  fillLayer.opacity = 0.5;
  [self.view.layer addSublayer:fillLayer];

}

• (void)drawRect:(CGRect)rect {
  //中间镂空的矩形框
  CGRect myRect =CGRectMake(100,100,200, 200);

  CGContextRef ctx = UIGraphicsGetCurrentContext();

  //背景色
  //[[UIColor colorWithPatternImage:[UIImage imageNamed:@"1.jpg"]] set];
  [[UIColor colorWithWhite:0 alpha:0.5] set];
  CGContextAddRect(ctx, rect);
  CGContextFillPath(ctx);

  //设置清空模式
  /**
  kCGBlendModeClear,
  kCGBlendModeCopy,
  kCGBlendModeSourceIn,
  kCGBlendModeSourceOut,
  kCGBlendModeSourceAtop,
  kCGBlendModeDestinationOver,
  kCGBlendModeDestinationIn,
  kCGBlendModeDestinationOut,
  kCGBlendModeDestinationAtop,
  kCGBlendModeXOR,
  kCGBlendModePlusDarker,
  kCGBlendModePlusLighter
  */
  CGContextSetBlendMode(ctx, kCGBlendModeClear);

  //画圆
  CGContextAddEllipseInRect(ctx, myRect);

  //填充
  CGContextFillPath(ctx);

}