Layer Filters - Core Animation - page 104

LISTING 6-13 Ripple Layer Implementation

@interface RippleLayer : CALayer {

}

@end

@implementation RippleLayer

+ ( id < CAAction >)defaultActionForKey:( NSString *)key;
{
if ( [key isEqualToString @”bounds” ] )
{
// Going to cheat a little bit here. Since this is a class
// method, we can't get the dimensions from self. Instead,
// we need to obtain this size some other way in a real-world
// application.
float w = 480.0;
float h = 360.0;

NSURL *url = [ NSURL fileURLWithPath :
[[ NSBundle mainBundle ]
pathForResource : @”Shading”
ofType : @”tiff” ]];

CIImage *shadingImage =
[[CIImage alloc ] initWithContentsOfURL : url];

CIFilter *rippleFilter =
[CIFilter filterWithName: @”CIRippleTransition” ];
[rippleFilter setDefaults];
[rippleFilter setValue :shadingImage
forKey : @”inputShadingImage” ];

[rippleFilter setValue :[CIVector vectorWithX: 0.5*w Y: 0.5*h]
forKey : @”inputCenter” ];

CATransition *theTransition=[ CATransition animation ];
[theTransition setFilter :rippleFilter];
[theTransition setDuration :2.0f];
return theTransition;

}