iOS核心动画高级技巧03-寄宿图

引入两个类拓展 UIView+LM.h 和 CALayer+LMXYWH.h
http://www.jianshu.com/p/03d38e6e25f9

#import "ViewController.h"

@interface ViewController ()<CALayerDelegate>
@property (strong,nonatomic)UIView *layerView;
@end

@implementation ViewController
#pragma mark - 控制器生命周期
- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self setupUI];
}
#pragma mark - setupUI
-(void)setupUI
{
    self.view.backgroundColor = [UIColor grayColor];
    
    self.layerView = [[UIView alloc]init];
    self.layerView.backgroundColor = [UIColor whiteColor];
    self.layerView.W = 200;
    self.layerView.H = 200;
    self.layerView.center = SCREEN_CENTER;
    [self.view addSubview:self.layerView];

    //CALayer 的 contents 属性 展示一张图片
    UIImage *image = [UIImage imageNamed:@"girl1.jpeg"];
    self.layerView.layer.contents = (__bridge id)image.CGImage;
    
     //1.1
     //contentsGravity 决定内容在图层的边界中的对齐方式
     self.layerView.layer.contentsGravity = kCAGravityResizeAspect;
     
     //contentsScale 目的不是放大！！
     //contentsGravity 会影响 contentsScale
     //contentsScale 用来判断在绘制图层的时候应该为寄宿图创建的空间大小， 和需要显示的图片的拉伸度，类似于UIView中的contentScaleFactor
    
    /**
     //1.2
     self.layerView.layer.contentsGravity =kCAGravityCenter;
     self.layerView.layer.contentsScale = image.scale;
     
     //2 maskToBounds
     self.layerView.layer.masksToBounds = YES;
     */
    
    //3 contentsRect 显示寄宿图中一个子域 0-1之间 是相对值
    //self.layerView.layer.contentsRect = CGRectMake(0, 0, 0.5, 0.5);
    
    //4 contentsCenter 在 Interface Builder 里可以配置 Stretching
//    self.layerView.layer.contentsCenter = CGRectMake(0.25, 0.25, 0.5, 0.5);
}
@end

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