图片剪裁

• (void)clipCircle
  {
  // 圆环的宽度
  CGFloat borderW = 5;
  // 加载旧的图片
  UIImage *oldImage = [UIImage imageNamed:@”阿狸头像”];
  // 新的图片尺寸
  CGFloat imageW = oldImage.size.width + 2 * borderW;
  CGFloat imageH = oldImage.size.height + 2 * borderW;
  // 设置新的图片尺寸
  CGFloat circirW = imageW > imageH ? imageH : imageW;
  // 开启上下文
  UIGraphicsBeginImageContextWithOptions(CGSizeMake(circirW, circirW), NO, 0.0);
  // 画大圆
  UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, circirW, circirW)];
  // 获取当前上下文
  CGContextRef ctx = UIGraphicsGetCurrentContext();
  // 添加到上下文
  CGContextAddPath(ctx, path.CGPath);
  [[UIColor whiteColor] set];
  // 渲染
  CGContextFillPath(ctx);
  CGRect clipR = CGRectMake(borderW, borderW, oldImage.size.width, oldImage.size.height);
  // 画圆：正切于旧图片的圆
  UIBezierPath *clipPath = [UIBezierPath bezierPathWithOvalInRect:clipR];
  // 设置裁剪区域
  [clipPath addClip];
  // 画图片
  [oldImage drawAtPoint:CGPointMake(borderW, borderW)];
  // 获取新的图片
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  // 关闭上下文
  UIGraphicsEndImageContext();
  _imageView.image = newImage;
  }

• (void)clip
  {
  // 1.加载旧的图片
  UIImage *oldImage = [UIImage imageNamed:@”阿狸头像”];
  // 2.开启上下文
  UIGraphicsBeginImageContextWithOptions(oldImage.size, NO, 0.0);
  // 3.画圆：正切于上下文
  UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, oldImage.size.width, oldImage.size.height)];
  // 4.设为裁剪区域
  [path addClip];
  // 5.画图片
  [oldImage drawAtPoint:CGPointZero];
  // 6.生成一个新的图片
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  // 7.关闭上下文
  UIGraphicsEndImageContext();
  }