Ios8 iOS：如何将默认相机图像裁剪为圆形

我在应用程序中使用的是ios默认摄像头。我想更改用户拍照后显示的“编辑”视图中的某些内容。通常，它会显示一个要裁剪的矩形，但我希望它显示一个圆形。如何进行此操作。

以下是可能有助于创建裁剪覆盖的解决方案：-

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if ([navigationController.viewControllers count] == 3)
    {
        CGFloat screenHeight = [[UIScreen mainScreen] bounds].size.height;

        UIView *plCropOverlay = [[[viewController.view.subviews objectAtIndex:1]subviews] objectAtIndex:0];

        plCropOverlay.hidden = YES;

        int position = 0;

        if (screenHeight == 568)
        {
            position = 124;
        }
        else
        {
            position = 80;
        }

        CAShapeLayer *circleLayer = [CAShapeLayer layer];

        UIBezierPath *path2 = [UIBezierPath bezierPathWithOvalInRect:
                               CGRectMake(0.0f, position, 320.0f, 320.0f)];
        [path2 setUsesEvenOddFillRule:YES];

        [circleLayer setPath:[path2 CGPath]];

        [circleLayer setFillColor:[[UIColor clearColor] CGColor]];
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 320, screenHeight-72) cornerRadius:0];

        [path appendPath:path2];
        [path setUsesEvenOddFillRule:YES];

        CAShapeLayer *fillLayer = [CAShapeLayer layer];
        fillLayer.path = path.CGPath;
        fillLayer.fillRule = kCAFillRuleEvenOdd;
        fillLayer.fillColor = [UIColor blackColor].CGColor;
        fillLayer.opacity = 0.8;
        [viewController.view.layer addSublayer:fillLayer];

        UILabel *moveLabel = [[UILabel alloc]initWithFrame:CGRectMake(0, 10, 320, 50)];
        [moveLabel setText:@"Move and Scale"];
        [moveLabel setTextAlignment:NSTextAlignmentCenter];
        [moveLabel setTextColor:[UIColor whiteColor]];

        [viewController.view addSubview:moveLabel];
    }
}

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可能重复：此代码将默认摄影机设置为圆形，但我希望打开默认摄影机，然后单击图片后，我希望裁剪为圆形。