如何从框架的原始中心放大/缩小绘制的圆圈？

Question

我想根据pinchGestureRecognizer捕获的用户的pinchGesture，增加或减少从原始帧的中心点扩展的绘制圆的大小。

到目前为止，我所遇到的问题是令人信服地展示了从中心出来的圈子的扩展。我可以让圆圈展开，但它似乎总是从左上角而不是中心扩展。我附上说明问题的屏幕截图：

以下是我绘制圆圈的代码：

    int size = 120;
    int radius = size/2;

    self.tapSelectionView = [[UIView alloc] initWithFrame:CGRectMake(longPressedPoint.x - radius, longPressedPoint.y - radius, size, size)];
    self.tapSelectionView.layer.cornerRadius = radius;
    self.tapSelectionView.layer.borderColor = [UIColor greenColor].CGColor;
    self.tapSelectionView.backgroundColor = [UIColor clearColor];
    self.tapSelectionView.layer.borderWidth = 2;
    [self.view addSubview:self.tapSelectionView];

    CGPoint centerOfOriginalFrame = CGPointMake(self.tapSelectionView.frame.origin.x + radius, self.tapSelectionView.frame.origin.y + radius);
    centerOfDrawnCircle = centerOfOriginalFrame;

在我的捏手势方法中，这就是我正在做的事情：

- (void)pinchGesture: (UIPinchGestureRecognizer *)pinchGestureRecognizer
{
    int size = 120;
    int radius = size/2;

    self.tapSelectionView.layer.cornerRadius = pinchGestureRecognizer.scale * radius;
    self.tapSelectionView.frame = CGRectMake(centerOfDrawnCircle.x - radius, centerOfDrawnCircle.y - radius, size * pinchGestureRecognizer.scale, size * pinchGestureRecognizer.scale);
}

谢谢！

Answer 1

self.tapSelectionView.layer.cornerRadius = pinchGestureRecognizer.scale * radius;
self.tapSelectionView.frame = CGRectMake(centerOfDrawnCircle.x - radius * pinchGestureRecognizer.scale, centerOfDrawnCircle.y - radius * pinchGestureRecognizer.scale, size * pinchGestureRecognizer.scale, size * pinchGestureRecognizer.scale);