为视图添加倒影效果

const CGFloat kReflectPercent = -0.25f;
const CGFloat kReflectOpacity = 0.3f;
const CGFloat kReflectDistance = 10.0f;
+ (void) addSimpleReflectionToView: (UIView *) theView
{
CALayer *reflectionLayer = [CALayer layer];
reflectionLayer.contents = [theView layer].contents;
reflectionLayer.opacity = kReflectOpacity;
reflectionLayer.frame = CGRectMake(0.0f, 0.0f,
theView.frame.size.width, theView.frame.size.height *
kReflectPercent);
CATransform3D stransform = CATransform3DMakeScale(1.0f, -1.0f,
1.0f);
CATransform3D transform = CATransform3DTranslate(stransform, 0.0f,
-(kReflectDistance + theView.frame.size.height), 0.0f);
reflectionLayer.transform = transform;
reflectionLayer.sublayerTransform = reflectionLayer.transform;
[[theView layer] addSublayer:reflectionLayer];
}

使用Core Graphics创建倒影：

+ (CGImageRef) createGradientImage: (CGSize)size
{
CGFloat colors[] = {0.0, 1.0, 1.0, 1.0};
// Create gradient in gray device color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray();
CGContextRef context = CGBitmapContextCreate(nil, size.width,
size.height, 8, 0, colorSpace, kCGImageAlphaNone);
CGGradientRef gradient =
CGGradientCreateWithColorComponents(colorSpace, colors,
NULL, 2);
CGColorSpaceRelease(colorSpace);
// Draw the linear gradient
CGPoint p1 = CGPointZero;
CGPoint p2 = CGPointMake(0, size.height);
CGContextDrawLinearGradient(context, gradient, p1, p2,
kCGGradientDrawsAfterEndLocation);
// Return the CGImage
CGImageRef theCGImage = CGBitmapContextCreateImage(context);
CFRelease(gradient);
CGContextRelease(context);
return theCGImage;
}
// Create a shrunken frame for the reflection
+ (UIImage *) reflectionOfView: (UIView *)theView
withPercent: (CGFloat) percent
{
// Retain the width but shrink the height
CGSize size = CGSizeMake(theView.frame.size.width,
theView.frame.size.height * percent);
// Shrink the view
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
[theView.layer renderInContext:context];
UIImage *partialimg =
UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// build the mask
CGImageRef mask = [ImageHelper createGradientImage:size];
CGImageRef ref = CGImageCreateWithMask(partialimg.CGImage, mask);
UIImage *theImage = [UIImage imageWithCGImage:ref];
CGImageRelease(ref);
CGImageRelease(mask);
return theImage;
}
const CGFloat kReflectDistance = 10.0f;
+ (void) addReflectionToView: (UIView *) theView
{
theView.clipsToBounds = NO;
UIImageView *reflection = [[UIImageView alloc] initWithImage:
[ImageHelper reflectionOfView:theView withPercent: 0.45f]];
CGRect frame = reflection.frame;
frame.origin = CGPointMake(0.0f, theView.frame.size.height +
kReflectDistance);
reflection.frame = frame;
// add the reflection as a simple subview
[theView addSubview:reflection];
[reflection release];
}