UIBezierPath 圆角

    // Begin a new image that will be the new image with the rounded corners
    // (here with the size of an UIImageView)
    UIGraphicsBeginImageContextWithOptions(_imagV.bounds.size, NO, 1.0);
    
    // Add a clip before drawing anything, in the shape of an rounded rect
    [[UIBezierPath bezierPathWithRoundedRect:_imagV.bounds
                                cornerRadius:50.0] addClip];
    // Draw your image
    [_imagV.image drawInRect:_imagV.bounds];
    
    // Get the image, here setting the UIImageView image
    _imagV.image = UIGraphicsGetImageFromCurrentImageContext();
    
    // Lets forget about that we were drawing
    UIGraphicsEndImageContext();