用鼠标绘制矩形，同时保持给定的比例

Question

我有一个我认为让我挠头的基本问题。

我希望能够在我的窗体上绘制一个矩形，同时将其限制为给定的比例。类似于Photoshop的裁剪工具的工作方式。

我可以使用比率正确缩放图像，但是在将公式应用于"实时"绘制的矩形时遇到问题。

这是绘制所述矩形的基本工作代码。

Public Class Form2
Dim mRect As Rectangle
Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
mRect = New Rectangle(e.X, e.Y, 0, 0)
Me.Invalidate()
End Sub
Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)
If e.Button = Windows.Forms.MouseButtons.Left Then
mRect = New Rectangle(mRect.Left, mRect.Top, e.X - mRect.Left, e.Y - mRect.Top)
Me.Invalidate()
End If
End sub
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
Using pen As New Pen(Color.Red, 3)
e.Graphics.DrawRectangle(pen, mRect)
End Using
End class

上面的代码可以很好地绘制一个自由形式的矩形。我只是不确定在哪里或如何应用公式以确保绘制的矩形始终遵循给定的比例，例如 1.5

任何帮助将不胜感激。谢谢

Answer 1

试试这个;

 Dim mRect As Rectangle
 Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
     mRect = New Rectangle(e.X, e.Y, 0, 0)
     Me.Invalidate()
 End Sub
 Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)
     If e.Button = Windows.Forms.MouseButtons.Left Then
         mRect = New Rectangle(mRect.Left, mRect.Top, e.X - mRect.Left, e.Y - mRect.Top)
         'Replace 1.5 with the scale you want to use
         Dim hgt As Integer = Convert.ToInt32(mRect.Height/1.5)
         Dim wdth As Integer = Convert.ToInt32(mRect.Width/1.5)
         mRect.Size = New Size(wdth*1.5, hgt*1.5)
         Me.Invalidate()
     End If
 End sub
 Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
     Using pen As New Pen(Color.Red, 3)
         e.Graphics.DrawRectangle(pen, mRect)
     End Using
 End class