将椭圆的原点放在WPF的中央

问题描述

我有一个程序，可以在 Canvas System.Windows.Shapes.Ellipse 的大小c>面板。

I have a program that I can drag, rotate and resize a System.Windows.Shapes.Ellipse in a Canvas panel.

要在画布内调整椭圆的大小并拖动它并使其始终居中，我需要每次校正时都要校正，因为椭圆的起点是

To resize and drag the ellipse inside the canvas and always keep it center I need to correct every time its origin, because the ellipse has it origin in the top left corner.

有没有办法默认使 Ellipse 的原点居中？

Have a way to make the origin in the Ellipse on center by default?

拖动：

Canvas.SetTop(ellipse, newX - (ellipse.Height / 2));
Canvas.SetLeft(ellipse, newY - (ellipse.Width / 2));

调整大小：

ellipse.Height = newHeight;
ellipse.Width = newWidth;

旋转：

ellipse.RenderTransform = new RotateTransform(angle,(ellipse.Width/2),(ellipse.Height/2));

推荐答案

如果宽度和高度固定，则最简单的解决方案将使用 X RenderTransform 设置为 TranslateTransform >和 Y 设置为负偏移量，分别等于椭圆的宽度和高度的一半：

If the width and height are fixed, the simplest solution would be to set the Ellipse's RenderTransform to a TranslateTransform with X and Y set to negative offsets equal to half the ellipse's width and height, respectively:

<Ellipse Width="100" Height="100" Fill="Red">
  <Ellipse.RenderTransform>
    <TranslateTransform X="-50" Y="-50" />
  </Ellipse.RenderTransform>
</Ellipse>

请注意，使用 RenderTransform 的警告是该转换不会应用于布局（并且 LayoutTransform 您不能使用 TranslateTransform ）。对于 Canvas 来说，这不应该是一个问题，因为它处理布局的方式虽然对其他面板也可能有问题。

Note that a caveat of using RenderTransform is that the transform is not applied to layout (and you cannot use a TranslateTransform for the LayoutTransform). That shouldn't be an issue with a Canvas because of how it handles layout, though it might be problematic with other panels.

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