如何平铺CALayer的内容？

Question

我想在CALayer上绘制一个CGImage,但它似乎只想拉伸它.

示例代码:

 self.background = [UIImage imageNamed: @"Background.png"];
 [documentDisplay.layer setContents: self.background.CGImage];

如果可以,我想避免继承子类.

Answer 1

您可以使用图案图像创建颜色,并将其设置为图层的背景颜色.

要做到这一点,你需要换你CGImage的CGPattern,并作出CGColor如此.

// callback for CreateImagePattern.
static void drawPatternImage (void *info, CGContextRef ctx)
{
    CGImageRef image = (CGImageRef) info;
    CGContextDrawImage(ctx, 
                       CGRectMake(0,0, CGImageGetWidth(image),CGImageGetHeight(image)),
                       image);
}

// callback for CreateImagePattern.
static void releasePatternImage( void *info )
{
    CGImageRelease((CGImageRef)info);
}

//assume image is the CGImage you want to assign as the layer background
int width = CGImageGetWidth(image);
int height = CGImageGetHeight(image);
static const CGPatternCallbacks callbacks = {0, &drawPatternImage, &releasePatternImage};
CGPatternRef pattern = CGPatternCreate (image,
                        CGRectMake (0, 0, width, height),
                        CGAffineTransformMake (1, 0, 0, 1, 0, 0),
                        width,
                        height,
                        kCGPatternTilingConstantSpacing,
                        true,
                        &callbacks);
CGColorSpaceRef space = CGColorSpaceCreatePattern(NULL);
CGFloat components[1] = {1.0};
CGColorRef color = CGColorCreateWithPattern(space, pattern, components);
CGColorSpaceRelease(space);
CGPatternRelease(pattern);
yourLayer.backgroundColor = color; //set your layer's background to the image
CGColorRelease(color);

此代码是从GeekGameBoard示例代码修改的.

Answer 2

完成此任务的最简单的代码是:

CALayer *layer = [CALayer layer];
layer.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"background_tile"]].CGColor;