Ios 将形状的移动限制为UIImageView的尺寸

使用我遇到的一些代码在图像上绘制一个圆形。平移和挤压手势用于正在绘制的圆形状。形状的移动跨越UIImageView的维度，到达未显示图像的UI的其余部分。我尝试合并其他示例中使用的方法，其中需要平移和收缩限制，以便将圆形状的移动限制在UIImageView的边界内，但无法使其中任何一个正常工作。我知道我需要控制平移和收缩的中心和半径值，以便它们不会超出UIImageView的边界，但对于如何执行这一操作，我没有丝毫线索。附件是我正在使用的代码。谢谢你的帮助

-(void)setUpCropTool:(id)sender{

    // create layer mask for the image

    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    self.imageToBeCropped.layer.mask = maskLayer;
    self.maskLayer = maskLayer;

    // create shape layer for circle we'll draw on top of image (the boundary of the circle)

    CAShapeLayer *circleLayer = [CAShapeLayer layer];
    circleLayer.lineWidth = 50;
    circleLayer.fillColor = [[UIColor clearColor] CGColor];
    circleLayer.strokeColor = [[UIColor redColor] CGColor];
    [self.imageToBeCropped.layer addSublayer:circleLayer];
    self.circleLayer = circleLayer;

    // create circle path

    [self updateCirclePathAtLocation:CGPointMake(self.imageToBeCropped.bounds.size.width / 2.0, self.imageToBeCropped.bounds.size.height / 2.0) radius:self.imageToBeCropped.bounds.size.width/2.5];

    // create pan gesture

    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    pan.delegate = self;
    [self.imageToBeCropped addGestureRecognizer:pan];
    self.imageToBeCropped.userInteractionEnabled = YES;
    self.pan = pan;

    // create pan gesture

    UIPinchGestureRecognizer *pinch = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];
    pinch.delegate = self;
    [self.imageToBeCropped addGestureRecognizer:pinch];
    self.pinch = pinch;

}

- (void)updateCirclePathAtLocation:(CGPoint)location radius:(CGFloat)radius
{
    self.circleCenter = location;
    self.circleRadius = radius;

    UIBezierPath *path = [UIBezierPath bezierPath];
    [path addArcWithCenter:self.circleCenter
                    radius:self.circleRadius
                startAngle:0.0
                  endAngle:M_PI * 2.0
                 clockwise:YES];

    self.maskLayer.path = [path CGPath];
    self.circleLayer.path = [path CGPath];
}

#pragma mark - Gesture recognizers

- (void)handlePan:(UIPanGestureRecognizer *)gesture
{
    static CGPoint oldCenter;
    CGPoint tranlation = [gesture translationInView:gesture.view];

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        oldCenter = self.circleCenter;
    }

    CGPoint newCenter = CGPointMake(oldCenter.x + tranlation.x, oldCenter.y + tranlation.y);



        [self updateCirclePathAtLocation:newCenter radius:self.circleRadius];



}

- (void)handlePinch:(UIPinchGestureRecognizer *)gesture
{
    static CGFloat oldRadius;
    CGFloat scale = [gesture scale];

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        oldRadius = self.circleRadius;
    }

    CGFloat newRadius = oldRadius * scale;

    [self updateCirclePathAtLocation:self.circleCenter radius:newRadius];
}


#pragma mark - UIGestureRecognizerDelegate

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    if ((gestureRecognizer == self.pan   && otherGestureRecognizer == self.pinch) ||
        (gestureRecognizer == self.pinch && otherGestureRecognizer == self.pan))
    {
        return YES;
    }

    return NO;
}

---

尝试向平移处理代码添加一些附加约束。可能是这样的：

if (oldCenter.x + tranlation.x >= superView.frame.size.width - self.circleRadius
|| oldCenter.x + tranlation.x <= self.circleRadius)
{
    newCenter.x = oldCenter.x;
}
else
{
    newCenter.x = oldCenter.x + tranlation.x;
}

if（oldCenter.x+translation.x>=superView.frame.size.width-self.circleRadius
||oldCenter.x+translation.x