Inner Shadow in UILabel

is it possible to create such a UILabel with inner and outer shadow?

alt text http://dl.getdropbox.com/u/80699/Bildschirmfoto%202010-07-12%20um%2021.28.57.png

i only know shado开发者_运维技巧wColor and shadowOffset

zoomed:

alt text http://dl.getdropbox.com/u/80699/Bildschirmfoto%202010-07-12%20um%2021.39.56.png

thanks!

The answer by dmaclach is only suitable for shapes that can easily be inverted. My solution is a custom view that works with any shape and also text. It requires iOS 4 and is resolution independent.

First, a graphical explanation of what the code does. The shape here is a circle.

The code draws text with a white dropshadow. If it's not required, the code could be refactored further, because the dropshadow needs to be masked differently. If you need it on an older version of iOS, you would have to replace the block and use an (annoying) 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];
}

Although Steve's answer does work, it didn't scale to my particular case and so I ended up creating an inner shadow by applying a shadow to a CGPath after clipping my context:

CGContextRef context = UIGraphicsGetCurrentContext();

// clip context so shadow only shows on the inside
CGPathRef roundedRect = [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:4].CGPath;
CGContextAddPath(context, roundedRect);
CGContextClip(context);

CGContextAddPath(context, roundedRect);
CGContextSetShadowWithColor(UIGraphicsGetCurrentContext(), CGSizeMake(0, 0), 3, [UIColor colorWithWhite:0 alpha:1].CGColor);
CGContextSetStrokeColorWithColor(context, [UIColor colorWithWhite:0 alpha:1].CGColor);
CGContextStrokePath(context);

Which results in:

You can change the shadow offset and blur to change the shadow style. If you need it to be darker, you can also successively add and then stroke the same CGPath, which will make the shadows pile up.

I use FXLabel for inner shadow, look here https://github.com/nicklockwood/FXLabel.

Yes, I have a blog post about it here. The short answer is to borrow the JTAInnerShadowLayer from here, subclass UILabel, and change its layerclass by overriding + (Class)layerClass so that it returns JTAInnerShadowLayer class like this:

+ (Class)layerClass
{
  return [JTAInnerShadowLayer class];
}

Then in the init method for the layer set up the JTAInnerShadowLayer something like this:

[self setBackgroundColor:[UIColor clearColor]];
JTAInnerShadowLayer *innerShadow = (JTAInnerShadowLayer *)[self layer];
[innerShadow setClipForAnyAlpha:YES];
[innerShadow setOutsideShadowSize:CGSizeMake(0.0, 1.0) radius:1.0];
[innerShadow setInsideShadowSize:CGSizeMake (0.0, 4.0) radius:6.0];
/* Uncomment this to make the label also draw the text (won't work well
   with black text!*/
//[innerShadow drawOriginalImage];

(or just borrow the JTAIndentLabel class).

You will have to do your own custom drawing to get an inner shadow. There's no way currently to do it with a standard UILabel.

Here's a reasonable explanation on doing inner shadow with Quartz.

Inner shadow in Core Graphics

Try PaintCode trial version! For beginners, you'll learn how to create custom drawings. It's very nice! :3 You can use it for practice or for learning, but don't use it all the time, you should also learn how to create drawings on your own.

Disclaimer: I'm not an endorser, I was just amazed by my discovery. ;)