当蒙版图像为黑白时,我使用此功能：

- (UIImage *)maskImage:(UIImage *)image withMask:(UIImage *)maskImage {

    CGImageRef maskRef = maskImage.CGImage; 

    CGImageRef mask = CGImageMaskCreate(CGImageGetWidth(maskRef),CGImageGetHeight(maskRef),CGImageGetBitsPerComponent(maskRef),CGImageGetBitsPerPixel(maskRef),CGImageGetBytesPerRow(maskRef),CGImageGetDataProvider(maskRef),NULL,false);

    CGImageRef masked = CGImageCreateWithMask([image CGImage],mask);
    return [UIImage imageWithCGImage:masked];
}

但在我的情况下如何做到这一点？