用DrawingBrush从中心旋转RotateTransform

Question

我有一个指南针的UserControl，我想旋转。我试着把它从中心旋转，谷歌找到了很多关于使用RenderTransformOrigin="0.5,0.5"来实现这一点的参考资料。但这并不是因为某种原因。它只是旋转UserControl的角作为原点。

如果我在CenterX="150"和CenterY="150"中设置了UserControl，它就能工作。但是，我还必须将主窗口中的UserControl的高度和宽度设置为300。

在调用UserControl时，如何使UserControl从其中心点旋转，而不管设置的高度和宽度如何？我还希望在RenderTransformOrigin中设置UserControl，而不是在调用它时。

(简化) UserControl XAML：

<UserControl x:Class="Poseidon.Views.CompassUserControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:Poseidon.Views"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">

    <Grid>
        <Grid.Resources>
            <DrawingBrush x:Key="Compass_ver1">
                <DrawingBrush.Drawing>
                    <DrawingGroup>
                        <DrawingGroup.Children>
                            <GeometryDrawing Brush="#FF000000" Geometry="M 375.286,151.366C 486.487,151.366 576.634,241.513 576.634,352.714C 576.634,463.915 486.487,554.061 375.286,554.061C 264.085,554.061 173.939,463.915 173.939,352.714C 173.939,241.513 264.085,151.366 375.286,151.366 Z "/>
                            <GeometryDrawing Geometry="M 375.286,151.366C 486.487,151.366 576.634,241.513 576.634,352.714C 576.634,463.915 486.487,554.061 375.286,554.061C 264.085,554.061 173.939,463.915 173.939,352.714C 173.939,241.513 264.085,151.366 375.286,151.366 Z ">
                                <GeometryDrawing.Pen>
                                    <Pen Thickness="0.755907" LineJoin="Round" Brush="#FF000000"/>
                                </GeometryDrawing.Pen>
                            </GeometryDrawing>
                            <GeometryDrawing Brush="#FFFFFFFF" Geometry="M 382.484,188.872C 472.971,192.847 543.103,269.425 539.128,359.912C 535.153,450.399 458.575,520.531 368.088,516.556C 277.601,512.58 207.469,436.003 211.444,345.516C 215.42,255.029 291.997,184.897 382.484,188.872 Z "/>
                            <GeometryDrawing Geometry="M 382.484,188.872C 472.971,192.847 543.103,269.425 539.128,359.912C 535.153,450.399 458.575,520.531 368.088,516.556C 277.601,512.58 207.469,436.003 211.444,345.516C 215.42,255.029 291.997,184.897 382.484,188.872 Z ">
                                <GeometryDrawing.Pen>
                                    <Pen Thickness="0.755907" LineJoin="Round" Brush="#FF000000"/>
                                </GeometryDrawing.Pen>
                            </GeometryDrawing>
                            <GeometryDrawing Brush="#FF000000" Geometry="M 375.286,227.352L 389.511,202.805L 403.736,178.258L 375.286,178.258L 346.836,178.258L 361.061,202.805L 375.286,227.352 Z "/>
                            <GeometryDrawing Geometry="M 375.286,227.352L 389.511,202.805L 403.736,178.258L 375.286,178.258L 346.836,178.258L 361.061,202.805L 375.286,227.352 Z ">
                                <GeometryDrawing.Pen>
                                    <Pen Thickness="0.755907" LineJoin="Round" Brush="#FF000000"/>
                                </GeometryDrawing.Pen>
                            </GeometryDrawing>
                        </DrawingGroup.Children>
                    </DrawingGroup>
                </DrawingBrush.Drawing>
            </DrawingBrush>
        </Grid.Resources>
        <Rectangle Fill="{StaticResource Compass_ver1}">
            <Rectangle.RenderTransform>
                <RotateTransform Angle="{Binding FlightData.Value.Heading}" />
            </Rectangle.RenderTransform>
        </Rectangle>
    </Grid>
</UserControl>

主窗口XAML：

<local:CompassUserControl DataContext="{Binding Rov}" Height="100" Width="100" RenderTransformOrigin="0.5,0.5"/>

Answer 1

RenderTransformOrigin属性获取或设置由RenderTransform属性声明的任何转换的中心点，相对于应用转换的元素的界限：https://msdn.microsoft.com/en-us/library/system.windows.uielement.rendertransformorigin(v=vs.110).aspx

因此-正如@Maxim所建议的-您应该在您的RenderTransformOrigin中设置Rectangle元素的UserControl属性

<Rectangle Fill="{StaticResource Compass_ver1}" RenderTransformOrigin="0.5, 0.5">
    <Rectangle.RenderTransform>
        <RotateTransform Angle="{Binding FlightData.Value.Heading}" />
    </Rectangle.RenderTransform>
</Rectangle>