如何根据交叉区域屏蔽图像[上下文]？

Question

两个图像上下文不在同一位置，我希望其中一个图像上下文根据它们的交叉区域被遮挡

Answer 1

    UIImage *image1, *image2;

    /* .... */

    CALayer *maskLayer = [[CALayer alloc] init];
    [maskLayer setFrame:[image1 convertRect:image2.bounds fromView:image2]];
    maskLayer.backgroundColor=[[UIColor blackColor] CGColor];
    image1.layer.mask=maskLayer;
    [maskLayer release];

    maskLayer = [[CALayer alloc] init];
    [maskLayer setFrame:[image2 convertRect:image1.bounds fromView:image1]];
    maskLayer.backgroundColor=[[UIColor blackColor] CGColor];
    image2.layer.mask=maskLayer;
    [maskLayer release];