トランジションをつくろう．

無駄な作業になりそうだが…
すでにあるトランジションフィルタが気に入らなかったので…

フィルタを２つにした．
１．重ねる画像をズームブラーで動きを付ける．
２．背景画像に最小合成で（白を背景にして）合成．

ブラーの具合を時間にあわせて変化させてみた．

@implementation Transition
...
- (void)createTransitionFilter {
    {
        [_transitionFilter release];
        _transitionFilter = nil;
        NSRect rect = [_delegate bounds];
        _transitionFilter = [[CIFilter filterWithName:@"CIMinimumCompositing"] retain];
        [_transitionFilter setDefaults];
        [_transitionFilter setValue:_baseImage forKey:@"inputBackgroundImage"];
    }
    {
        [_transitionFilter2 release];
        _transitionFilter2 = nil;
        NSRect rect = [_delegate bounds];
        _transitionFilter2 = [[CIFilter filterWithName:@"CIZoomBlur"] retain];
        [_transitionFilter2 setDefaults];
        [_transitionFilter2 setValue:_overlayImage forKey:@"inputImage"];
        [_transitionFilter2 setValue:[CIVector vectorWithX:NSMidX(rect) Y:NSMidY(rect) Z:0 W:0] forKey:@"inputCenter"];
    }
}
- (void)draw:(NSRect)viewRect {
    NSRect rect = [_delegate bounds];
    float time = [_animation currentValue];
    if ([self reverse]) {
         time= 1.0 - time;
    }
    [_transitionFilter2 setValue:[NSNumber numberWithFloat:(time * 50.0)+10] forKey:@"inputAmount"];
    [_transitionFilter setValue:[_transitionFilter2 valueForKey:@"outputImage"] forKey:@"inputImage"];
    CIImage * outputCIImage = [_transitionFilter valueForKey:@"outputImage"];
    [outputCIImage drawInRect:rect fromRect:NSMakeRect(0, rect.size.height, rect.size.width, -rect.size.height) operation:NSCompositeSourceOver fraction:1.0];
}

＃すでに目的を見失っている気がする…