ios – 如何在CALayers上创建反向掩码

步骤1：创建没有任何Alpha通道的掩码.

步骤2：通过以下方法创建反转掩码

- (UIImage*) createInvertMask:(UIImage *)maskImage withTargetImage:(UIImage *) image {

CGImageRef maskRef = maskImage.CGImage;

CGBitmapInfo bitmapInfo = kCGImageAlphaNone;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;

CGImageRef mask = CGImageCreate(CGImageGetWidth(maskRef),CGImageGetHeight(maskRef),CGImageGetBitsPerComponent(maskRef),CGImageGetBitsPerPixel(maskRef),CGImageGetBytesPerRow(maskRef),CGColorSpaceCreateDeviceGray(),bitmapInfo,CGImageGetDataProvider(maskRef),nil,NO,renderingIntent);


CGImageRef masked = CGImageCreateWithMask([image CGImage],mask);

CGImageRelease(mask);
CGImageRelease(maskRef);

return [UIImage imageWithCGImage:masked];
}

步骤3：通过以下方法将反向掩码设置为UIView

-(void) maskWithImage:(UIImage*) maskImage TargetView:(UIView*) targetView{
CALayer *_maskingLayer = [CALayer layer];
_maskingLayer.frame = targetView.bounds;
[_maskingLayer setContents:(id)[maskImage CGImage]];
[targetView.layer setMask:_maskingLayer];
}

成品.

怎么打电话

UIImage* targetImage = [UIImage imagenamed:@"sky_bg.png"];
UIImage* mask = [UIImage imagenamed:@"mask01.png"];

UIImage* invertMask = [self createInvertMask:mask withTargetImage:targetImage];

[self maskWithImage:invertMask TargetView:targetview];