iOS Core Animation - 寄宿圖

contents屬性

CALayer的contents屬性，爲id類型，意味着可以是任何類型對象。中間需要做類型轉換。

layer.contents = (__bridge id)image.CGImage;//這是在ARC下

例如給view1加載一張圖片

UIImage *image = [UIImage imageNamed:@"p1.jpg"];

   self.view1.layer.contents = (__bridge id)image.CGImage;

圖片是鋪滿圖層的，可以設置contentGravity來改變加載狀況。

layer.contentsGravity = kCAGravityResizeAspect;

設置不同的contentsGravity值將達到不同的效果。

contentScale 屬性定義了寄宿圖像和視圖大小的比例。當用代碼設置寄宿圖像時，一定要設置contentScale屬性

blueLayer.contentsScale = [[UIScreen mainScreen] scale];

maskToBounds設置超出邊界部分是否顯示。

contentsRect 屬性允許我們在視圖層裏面線束寄宿圖像的一個子域。用於圖片分割

- (void)viewDidLoad {
    [super viewDidLoad];
   UIImage *image = [UIImage imageNamed:@"p1.jpg"];
    
    //圖片分割
    [self addSpriteImage:image WithContentReact:CGRectMake(0, 0, 0.5, 0.5) WithLayer:self.view1.layer];
    [self addSpriteImage:image WithContentReact:CGRectMake(0.5, 0, 0.5, 0.5) WithLayer:self.view3.layer];
    [self addSpriteImage:image WithContentReact:CGRectMake(0, 0.5, 0.5, 0.5) WithLayer:self.view2.layer];
    [self addSpriteImage:image WithContentReact:CGRectMake(0.5, 0.5, 0.5, 0.5) WithLayer:self.view4.layer];
    
}
-(void)addSpriteImage:(UIImage *)image WithContentReact:(CGRect)react WithLayer:(CALayer *)layer{
    layer.contents = (__bridge id)image.CGImage;
    layer.contentsRect =react;
    layer.contentsGravity = kCAGravityResizeAspect;
}

contentsCenter屬性用於設置圖層拉伸位置，定義了一個固定的邊框和一個在圖層上可拉伸區域

在CALayer上面繪製。要遵守CALayerDelegate代理協議，首先會生成一個上下文用於繪製。

-(void)addSpriteImage:(UIImage *)image WithContentReact:(CGRect)react WithLayer:(CALayer *)layer在此代理中繪製

- (void)viewDidLoad {
    [super viewDidLoad];


    CALayer *blueLayer = [CALayer layer];
    blueLayer.backgroundColor = [UIColor blueColor].CGColor;
    blueLayer.frame = CGRectMake(50, 50, 100, 100);
    blueLayer.contentsScale = [[UIScreen mainScreen] scale];
    [self.view1.layer addSublayer:blueLayer];
     blueLayer.delegate = self;
    [blueLayer display];
    
}
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx{
    CGContextSetLineWidth(ctx, 10.0);
    CGContextSetStrokeColorWithColor(ctx, [UIColor redColor].CGColor);
    CGContextStrokeEllipseInRect(ctx, layer.bounds);
    
}