DrawingGroup与DrawingVisual变换

Question

我有两种方法可以在屏幕上绘制一个旋转的矩形。

RenderMethod1使用DrawingVisual

渲染一个旋转30度的矩形

private static void RenderMethod1(DrawingContext dc) {
    DrawingVisual drawingVisual = new DrawingVisual();
    using (DrawingContext context = drawingVisual.RenderOpen()) {
        Rect rect = new Rect(new System.Windows.Point(100, 100), new System.Windows.Size(320, 80));
        context.DrawRectangle(System.Windows.Media.Brushes.LightBlue, (System.Windows.Media.Pen)null, rect);
    }
    drawingVisual.Transform = new RotateTransform(30, 100, 100);
    dc.DrawDrawing(drawingVisual.Drawing);
}

RenderMethod2使用DrawingGroup

渲染一个旋转30度的矩形

    private static void RenderMethod2(DrawingContext dc) {
        DrawingGroup group = new DrawingGroup();
        DrawingVisual drawingVisual = new DrawingVisual();
        using (DrawingContext context = drawingVisual.RenderOpen()) {
            Rect rect = new Rect(new System.Windows.Point(100, 100), new System.Windows.Size(320, 80));
            context.DrawRectangle(System.Windows.Media.Brushes.LightBlue, (System.Windows.Media.Pen)null, rect);
        }
        group.Children.Add(drawingVisual.Drawing);
        group.Transform = new RotateTransform(30, 100, 100);
        group.Freeze();
        dc.DrawDrawing(group);
    }

输出如下：

RenderMethod1

RenderMethod2 

正如您所看到的，RenderMethod1和RenderMethod2输出应该完全相同，但它们不是。在RenderMethod1中我有什么问题吗？

提前感谢您的帮助，

Answer 1

我终于通过更改RenderMethod1来解决问题，并按预期工作。

private static void RenderMethod1(DrawingContext dc) {
    DrawingGroup drawingVisual = new DrawingGroup();
    using (DrawingContext context = drawingVisual.Open()) {
        Rect rect = new Rect(new System.Windows.Point(100, 100), new System.Windows.Size(320, 80));
        context.DrawRectangle(System.Windows.Media.Brushes.LightBlue, (System.Windows.Media.Pen)null, rect);
    }
    drawingVisual.Transform = new RotateTransform(30, 100, 100);
    dc.DrawDrawing(drawingVisual);
}