IOS实现图片倒影效果

#import <QuartzCore/QuartzCore.h>
- (void)viewDidLoad
{
    [super viewDidLoad];

    
    [[[self view] layer] setBackgroundColor:[[UIColor blackColor] CGColor]]; 
    
    UIImage *balloon = [UIImage imageNamed:@"app3.png"];
    
    //图片层
    
    CALayer *topLayer = [[CALayer alloc] init]; 
    
    [topLayer setBounds:CGRectMake(0.0f, 0.0f, 320-100.0, 240-100)]; 
    
    [topLayer setPosition:CGPointMake(160.0f, 120.0f)]; 
    
    [topLayer setContents:(id)[balloon CGImage]];
    
    [[[self view] layer] addSublayer:topLayer];
    
    //图片阴影层
    
    CALayer *reflectionLayer = [[CALayer alloc] init]; 
    
    [reflectionLayer setBounds:CGRectMake(0.0f, 0.0f, 320.0-100, 240.0-100)]; 
    
    [reflectionLayer setPosition:CGPointMake(160.0f, 310.0f-100)];
    
    [reflectionLayer setContents:[topLayer contents]];
    
    [reflectionLayer setValue:[NSNumber numberWithFloat:180.0] forKeyPath:@"transform.rotation.x"];
    
    //渐变层
    
    CAGradientLayer *gradientLayer = [[CAGradientLayer alloc] init]; 
    
    [gradientLayer setBounds:[reflectionLayer bounds]]; 
    
    [gradientLayer setPosition:CGPointMake([reflectionLayer bounds].size.width/2, [reflectionLayer bounds].size.height/2)];
    
    [gradientLayer setColors:[NSArray arrayWithObjects: (id)[[UIColor clearColor] CGColor],(id)[[UIColor blackColor] CGColor], nil]];
    
    [gradientLayer setStartPoint:CGPointMake(0.5,0.35)]; 
    
    [gradientLayer setEndPoint:CGPointMake(0.5,1.0)];
    
    [reflectionLayer setMask:gradientLayer];
    
    [[[self view] layer] addSublayer:reflectionLayer];
	// Do any additional setup after loading the view, typically from a nib.
}