iOS之CATiledLayer的属性简介和使用

1、CATiledLayer简介　　

　　CATiledLayer用于大型图片进行分割显示，需要显示的图片才会加载，直接上代码：

- (void)viewDidLoad {

    [super viewDidLoad];

    [self cutImageAndSave];

    [self addTiledLayer];

}

- (void)drawLayer:(CATiledLayer *)layer inContext:(CGContextRef)ctx{

    CGRect bounds = CGContextGetClipBoundingBox(ctx);

    NSInteger x = floor(bounds.origin.x / layer.tileSize.width);

    NSInteger y = floor(bounds.origin.y / layer.tileSize.height);

    //load tile image

    NSString *filePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;

    NSString *imageName = [NSString stringWithFormat:@"%@/pic-%02ld-%02ld.png",filePath,x,y];

    UIImage *tileImage = [UIImage imageWithContentsOfFile:imageName];

    UIGraphicsPushContext(ctx);

    [tileImage drawInRect:bounds];

    UIGraphicsPopContext();

}

//添加CATiledLayer

- (void)addTiledLayer{

    UIScrollView *scrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(, , CScreenWidth, CScreenHeight)];

    [self.view addSubview:scrollView];

    UIImage *image = [UIImage imageNamed:@"pic1.jpg"];

    CATiledLayer *tiledLayer = [CATiledLayer layer];

    tiledLayer.frame = CGRectMake(, , image.size.width, image.size.height);

    tiledLayer.delegate = self;

    tiledLayer.tileSize = CGSizeMake(, );

    _tiledLayer = tiledLayer;

    scrollView.contentSize = tiledLayer.frame.size;

    [scrollView.layer addSublayer:tiledLayer];

    [tiledLayer setNeedsDisplay];

}

//切图保存到沙盒

- (void)cutImageAndSave{

    NSString *filePath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;

    NSString *imageName = [NSString stringWithFormat:@"%@/pic-00-00.png",filePath];

    UIImage *tileImage = [UIImage imageWithContentsOfFile:imageName];

    NSLog(@"%@",imageName);

    if (tileImage) return;

    UIImage *image = [UIImage imageNamed:@"pic1.jpg"];

    UIImageView *imageView = [[UIImageView alloc]initWithImage:image];

    CGFloat WH = ;

    CGSize size = image.size;

    NSInteger rows = ceil(size.height / WH);

    NSInteger cols = ceil(size.width / WH);

    for (NSInteger y = ; y < rows; ++y) {

        for (NSInteger x = ; x < cols; ++x) {

            UIImage *subImage = [self captureView:imageView frame:CGRectMake(x*WH, y*WH, WH, WH)];

            NSString *path = [NSString stringWithFormat:@"%@/pic-%02ld-%02ld.png",filePath,x,y];

            [UIImagePNGRepresentation(subImage) writeToFile:path atomically:YES];

        }

    }

}

//切图

- (UIImage*)captureView:(UIView *)theView frame:(CGRect)fra{

    //开启图形上下文 将heView的所有内容渲染到图形上下文中

    UIGraphicsBeginImageContext(theView.frame.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    [theView.layer renderInContext:context];

    //获取图片

    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    CGImageRef ref = CGImageCreateWithImageInRect(img.CGImage, fra);

    UIImage *i = [UIImage imageWithCGImage:ref];

    CGImageRelease(ref);

    return i;

}

效果图

2、CATiledLayer属性

#import <QuartzCore/CALayer.h>

NS_ASSUME_NONNULL_BEGIN

CA_CLASS_AVAILABLE (10.5, 2.0, 9.0, 2.0)

@interface CATiledLayer : CALayer

//初次加载淡入时间，默认0.25s

//由于是类方法，无法直接修改，创建子类进行方法覆盖就行。

+ (CFTimeInterval)fadeDuration;

//这两个属性用处不太懂？？？

/* The number of levels of detail maintained by this layer. Defaults to

 * one. Each LOD is half the resolution of the previous level. If too

 * many levels are specified for the current size of the layer, then

 * the number of levels is clamped to the maximum value (the bottom

 * most LOD must contain at least a single pixel in each dimension). */

@property size_t levelsOfDetail;

/* The number of magnified levels of detail for this layer. Defaults to

 * zero. Each previous level of detail is twice the resolution of the

 * later. E.g. specifying 'levelsOfDetailBias' of two means that the

 * layer devotes two of its specified levels of detail to

 * magnification, i.e. 2x and 4x. */

@property size_t levelsOfDetailBias;

//Defaults to (256, 256),设置CATiledLayer的item的大小

@property CGSize tileSize;

@end

NS_ASSUME_NONNULL_END