Draw rectangle with mouse while maintaining a given ratio - vb.net

Question

I have what I think is a basic problem that has me scratching my head.
I want to be able to draw a rectangle on my form while constraining it to a given ratio. Similar to how Photoshop's crop tool works.
I can scale images correctly using a ratio, but I am having trouble applying the formula to a 'live' drawn rectangle.
Here is the basic working code to draw said rectangle.
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
The above code works fine to draw a freeform rectangle. I'm just not sure where or how to apply the formula to ensure the drawn rectangle always adheres to a given ratio such as 1.5
Any help would be hugely appreciated. Thanks

Answer 1

Try this ;
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