Timer-Based Animation - iOS Core Animation - page 233

}
float interpolate( float from, float to, float time)
{
return (to - from) * time + from;
}
- ( id )interpolateFromValue:( id )fromValue
toValue:( id )toValue
time:( float )time
{
if ([fromValue isKindOfClass :[ NSValue class ]])
{
//get type
const char *type = [( NSValue *)fromValue objCType ];
if ( strcmp (type, @encode ( CGPoint )) == 0 )
{
CGPoint from = [fromValue CGPointValue ];
CGPoint to = [toValue CGPointValue ];
CGPoint result = CGPointMake ( interpolate (from. x , to. x , time),
interpolate (from. y , to. y , time));
return [ NSValue valueWithCGPoint :result];
}
}
//provide safe default implementation
return (time < 0.5 )? fromValue: toValue;
}
float bounceEaseOut( float t)
{
if (t < 4 / 11.0 )
{
return ( 121 * t * t)/ 16.0 ;
}
else if (t < 8 / 11.0 )
{
return ( 363 / 40.0 * t * t) - ( 99 / 10.0 * t) + 17 / 5.0 ;
}
else if (t < 9 / 10.0 )
{
return ( 4356 / 361.0 * t * t) - ( 35442 / 1805.0 * t) + 16061 / 1805.0 ;
}
return ( 54 / 5.0 * t * t) - ( 513 / 25.0 * t) + 268 / 25.0 ;
}