缩放图像锚定在某一点

Question

是否可以通过使用指定的点作为锚来缩放图像，即图像从这一点“增长”？

Answer 1

缩放不是基于一个观点。你想要做的是移动它，使新图像和原始图像上的对应点在同一点。为此，只需调整图像的（x，y）位置即可。使用与边缘成比例的距离乘以大小差异。

Answer 2

你可以做这样的事情（基于使用UIPinchGesureRecognize的解决方案，但你可以得到这个想法......）。 这是为gestureRecognizer调用的选择器：

CGPoint newDistanceFromCenter;
CGPoint distanceFromCenter;

- (void) scale:(id)sender
{
    UIPinchGestureRecognizer *recognizer = (UIPinchGestureRecognizer*)sender;

    if(recognizer.state == UIGestureRecognizerStateBegan)
    {
        CGPoint pinchPoint = [recognizer locationInView:self];
        distanceFromCenter.x = self.center.x - pinchPoint.x;
        distanceFromCenter.y = self.center.y - pinchPoint.y;
    }
    else if(recognizer.state == UIGestureRecognizerStateChanged) 
    {
        CGAffineTransform currentTransform = self.transform;
        CGFloat scale = recognizer.scale;

        newDistanceFromCenter.x = (distanceFromCenter.x * scale);
        newDistanceFromCenter.y = (distanceFromCenter.y * scale);

        CGPoint center = scalingImage_.center;
        center.x -= (distanceFromCenter.x - newDistanceFromCenter.x);
        center.y -= (distanceFromCenter.y - newDistanceFromCenter.y);
        self.center = center;

        distanceFromCenter = newDistanceFromCenter;

        self.transform = CGAffineTransformScale(currentTransform, scale, scale);

        recognizer.scale = 1;
    }
}