vb.net - 如何使用带有旋转和变换路径的 IsVisible 进行鼠标点击测试

Question

我正在使用 GDI+ 绘制可缩放矢量图形，并且需要在 mousemove 上进行 hitttest。我见过的所有例子都使用模型空间=世界空间，没有变换。这是问题的简化示例:

Imports System.Drawing.Drawing2D

Public Class Form1

  Private myrect As New GraphicsPath

  Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)

    ' The rectangle's centre is at 30,10. Move to origin to rotate
    e.Graphics.TranslateTransform(-30, -10, Drawing2D.MatrixOrder.Append)
    e.Graphics.RotateTransform(45, Drawing2D.MatrixOrder.Append)

    ' Move it back, 50x50 away from the origin 
    ' (80,60 because we moved -30,-10 to rotate)
    e.Graphics.TranslateTransform(80, 60, Drawing2D.MatrixOrder.Append)
    e.Graphics.DrawPath(New Pen(Brushes.Black, 2), myrect)

    ' ...loads more painting, many paths, many varying transformations

  End Sub

  Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
    Handles Me.Load

    ' Make a rectangle 60x20 with top-left corner at the origin
    myrect.AddLine(0, 0, 60, 0)
    myrect.AddLine(60, 0, 60, 20)
    myrect.AddLine(60, 20, 0, 20)
    myrect.CloseFigure()

    ' ...loads more shapes created here

  End Sub

  Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove

    ' Pretend that all the drawing stuff above happened some unspecified time ago, 
    ' in different assembly, written by a martian, in some other vile language.
    ' Obviously, his "e.graphics" has long since been garbage-collected.
    If myrect.IsVisible(e.Location) Then
        ' Works when moving over the path at the origin, ignores transforms.
        Debug.WriteLine("Over the rectangle at " & e.Location.ToString)
    End If

  End Sub

End Class

产生(鼠标移动为红色)

IsVisible 在原点附近启动，即矩形在变换之前的位置。

我知道如果我在 OnPaint 中使用图形，我可以用它来对变换进行 HitTest ，但黄金法则说“永远不要保存图形”。

非常欢迎任何建议。

---

事后分析:作为记录，这里是 Vincent 答案的实现，效果很好:

Imports System.Drawing.Drawing2D

Public Class Form1

  Private myrect As New GraphicsPath
  Private mytransform As Matrix

  Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)

    ' The rectangle's centre is at 30,10. Move to origin to rotate
    e.Graphics.TranslateTransform(-30, -10, Drawing2D.MatrixOrder.Append)
    e.Graphics.RotateTransform(45, Drawing2D.MatrixOrder.Append)

    ' Move it back, 50x50 away from the origin 
    ' (80,60 because we moved -30,-10 to rotate)
    e.Graphics.TranslateTransform(80, 60, Drawing2D.MatrixOrder.Append)
    e.Graphics.DrawPath(New Pen(Brushes.Black, 2), myrect)
    mytransform = e.Graphics.Transform

    ' ...loads more painting, many paths, many varying transformations

  End Sub

  Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
    Handles Me.Load

    ' Make a rectangle 60x20 with top-left corner at the origin
    myrect.AddLine(0, 0, 60, 0)
    myrect.AddLine(60, 0, 60, 20)
    myrect.AddLine(60, 20, 0, 20)
    myrect.CloseFigure()

    ' ...loads more shapes created here

  End Sub

  Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove

    mytransform.Invert()
    Dim mouseat() As Point = {e.Location}
    mytransform.TransformPoints(mouseat)
    If myrect.IsVisible(mouseat(0)) Then
        ' Works when moving over the path at the origin, ignores transforms.
        Debug.WriteLine("Over the rectangle at " & e.Location.ToString)
    End If

  End Sub

End Class

Answer 1

ScaleTransform 和 TranslateTransform 方法更改 Graphics.Matrix 属性。如果您想保留这一点，那么将相同的变换应用于鼠标位置将会非常方便。由于您将变换应用于各个形状，因此您需要存储每个形状的矩阵。

Matrix.TransformPoints() 就可以解决您的问题。