iphone - UILabel中的内部阴影

是否可以创建这样一个内部和外部阴影的uilabel？
alt text http://dl.getdropbox.com/u/80699/Bildschirmfoto%202010-07-12%20um%2021.28.57.png
我只知道shadowColor和shadowOffset
缩放：
alt text http://dl.getdropbox.com/u/80699/Bildschirmfoto%202010-07-12%20um%2021.39.56.png
谢谢！

最佳答案

dmaclach的答案只适用于容易反转的形状。我的解决方案是使用任意形状和文本的自定义视图。它需要ios 4，并且与分辨率无关。
首先，对代码的作用进行图形化解释。这里的形状是一个圆。
代码用白色的dropshadow绘制文本。如果不需要，可以进一步重构代码，因为dropshadow需要以不同的方式进行屏蔽。如果需要在较旧版本的ios上使用，则必须替换块并使用（恼人的）cgbitmapcontext。

- (UIImage*)blackSquareOfSize:(CGSize)size {
  UIGraphicsBeginImageContextWithOptions(size, NO, 0);
  [[UIColor blackColor] setFill];
  CGContextFillRect(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, size.width, size.height));
  UIImage *blackSquare = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  return blackSquare;
}


- (CGImageRef)createMaskWithSize:(CGSize)size shape:(void (^)(void))block {
  UIGraphicsBeginImageContextWithOptions(size, NO, 0);
  block();
  CGImageRef shape = [UIGraphicsGetImageFromCurrentImageContext() CGImage];
  UIGraphicsEndImageContext();
    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(shape),
                                      CGImageGetHeight(shape),
                                      CGImageGetBitsPerComponent(shape),
                                      CGImageGetBitsPerPixel(shape),
                                      CGImageGetBytesPerRow(shape),
                                      CGImageGetDataProvider(shape), NULL, false);
  return mask;
}


- (void)drawRect:(CGRect)rect {
  UIFont *font = [UIFont fontWithName:@"HelveticaNeue-Bold" size:40.0f];
  CGSize fontSize = [text_ sizeWithFont:font];

  CGImageRef mask = [self createMaskWithSize:rect.size shape:^{
    [[UIColor blackColor] setFill];
    CGContextFillRect(UIGraphicsGetCurrentContext(), rect);
    [[UIColor whiteColor] setFill];
    // custom shape goes here
    [text_ drawAtPoint:CGPointMake((self.bounds.size.width/2)-(fontSize.width/2), 0) withFont:font];
    [text_ drawAtPoint:CGPointMake((self.bounds.size.width/2)-(fontSize.width/2), -1) withFont:font];
  }];

  CGImageRef cutoutRef = CGImageCreateWithMask([self blackSquareOfSize:rect.size].CGImage, mask);
  CGImageRelease(mask);
  UIImage *cutout = [UIImage imageWithCGImage:cutoutRef scale:[[UIScreen mainScreen] scale] orientation:UIImageOrientationUp];
  CGImageRelease(cutoutRef);

  CGImageRef shadedMask = [self createMaskWithSize:rect.size shape:^{
    [[UIColor whiteColor] setFill];
    CGContextFillRect(UIGraphicsGetCurrentContext(), rect);
    CGContextSetShadowWithColor(UIGraphicsGetCurrentContext(), CGSizeMake(0, 1), 1.0f, [[UIColor colorWithWhite:0.0 alpha:0.5] CGColor]);
    [cutout drawAtPoint:CGPointZero];
  }];

  // create negative image
  UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0);
  [[UIColor blackColor] setFill];
  // custom shape goes here
  [text_ drawAtPoint:CGPointMake((self.bounds.size.width/2)-(fontSize.width/2), -1) withFont:font];
  UIImage *negative = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();

  CGImageRef innerShadowRef = CGImageCreateWithMask(negative.CGImage, shadedMask);
  CGImageRelease(shadedMask);
  UIImage *innerShadow = [UIImage imageWithCGImage:innerShadowRef scale:[[UIScreen mainScreen] scale] orientation:UIImageOrientationUp];
  CGImageRelease(innerShadowRef);

  // draw actual image
  [[UIColor whiteColor] setFill];
  [text_ drawAtPoint:CGPointMake((self.bounds.size.width/2)-(fontSize.width/2), -0.5) withFont:font];
  [[UIColor colorWithWhite:0.76 alpha:1.0] setFill];
  [text_ drawAtPoint:CGPointMake((self.bounds.size.width/2)-(fontSize.width/2), -1) withFont:font];

  // finally apply shadow
  [innerShadow drawAtPoint:CGPointZero];
}

关于iphone - UILabel中的内部阴影，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/3231690/