Drawing rect in picturebox not done to right scale for mouse - vb.net

Question

I currently have a picture box where the user will click and drag to draw a rectangle over an image (one that can be changed regularly). When they're done (mouse_up), I will display the relative points of the rect in a text box to the resolution.
So, for example, the user draws from top left (0,0) to bottom right of a 1920 x 680 image (picturebox.right, picturebox.bottom) for a rect, the text box will show (1920,680) for the end point. That's mostly just ratio stuff.
I am using the code from an answer of a previous question of mine (Having trouble drawing simple rectangle in picturebox) to draw it.
The Problem: The box doesn't follow the mouse since the images have to be done in stretch mode. They're usually pretty large (like 1920 x 680) and can't fit in a regular gui. There are multiple resolutions, so got to go dynamic with the ratios. Without editing, this code works great in normal mode, but that doesn't work for usability. So, when you draw the box, it's really small and not relative to the mouse (so I can't display the end point on the textboxes).
Here's an example of what I mean. I've dragged my mouse halfway across the image:
What I've tried: I've attempted to counter act it by ratios, but it still doesn't fix the displaying the end point issue, or does it really follow the mouse that well. It's usually off by at least 10 or so pixels to the left. Here's my adjusted code for that:
Private Sub DrawRectangle(ByVal pnt As Point)
Try
Dim g As Graphics
g = Graphics.FromImage(img)
g.DrawImage(imgClone, 0, 0) 'we are clearing img with imgClone. imgClone contains the original image without the rectangles
Dim w_ratio As Integer = Math.Floor(img.Width / pbZoneImage.Width)
Dim h_ratio As Integer = Math.Floor(img.Height / pbZoneImage.Height)
Dim customPen As New Pen(currentColor, 5)
'If pnt.X = mouse_Down.X Or pnt.Y = mouse_Down.Y Then
' g.DrawLine(customPen, mouse_Down.X, mouse_Down.Y, pnt.X * w_ratio, pnt.Y * h_ratio)
'Else
theRectangle = New Rectangle(Math.Min(mouse_Down.X, pnt.X * w_ratio), Math.Min(mouse_Down.Y, pnt.Y * h_ratio),
Math.Abs(mouse_Down.X - pnt.X * w_ratio), Math.Abs(mouse_Down.Y - pnt.Y * h_ratio))
g.DrawRectangle(customPen, theRectangle)
'End If
g.Dispose()
pbZoneImage.Invalidate() 'draw img to picturebox
Catch ex As Exception
End Try
End Sub
I've also tried just getting the end display point (x,y) to match the relative end of the rectangle, but again it isn't working with the ratios.
Any ideas on how to make this work as well as it does in normal mode as it does in stretch? I'm also open to different controls or just any tips in general. Thanks!

Answer 1

This can be done with many ways but the easiest is to use a picturebox with SizeMode = Normal. Load your images:
img = New Bitmap(pbZoneImage.Width, pbZoneImage.Height)
imgClone = My.Resources.... 'real dimensions
Dim g As Graphics = Graphics.FromImage(img)
'it will scale the image, no need for stretch mode
g.DrawImage(imgClone, 0, 0, pbZoneImage.Width, pbZoneImage.Height)
g.Dispose()
pbZoneImage.Image = img
Then draw normally:
Private Sub DrawRectangle(ByVal pnt As Point)
Try
Dim g As Graphics
g = Graphics.FromImage(img)
g.DrawImage(imgClone, 0, 0, pbZoneImage.Width, pbZoneImage.Height) 'we are clearing img with imgClone. imgClone contains the original image without the rectangles
Dim customPen As New Pen(currentColor, 5)
'If pnt.X = mouse_Down.X Or pnt.Y = mouse_Down.Y Then
' g.DrawLine(customPen, mouse_Down.X, mouse_Down.Y, pnt.X * w_ratio, pnt.Y * h_ratio)
'Else
theRectangle = New Rectangle(Math.Min(mouse_Down.X, pnt.X), Math.Min(mouse_Down.Y, pnt.Y),
Math.Abs(mouse_Down.X - pnt.X), Math.Abs(mouse_Down.Y - pnt.Y))
g.DrawRectangle(customPen, theRectangle)
'End If
g.Dispose()
pbZoneImage.Invalidate() 'draw img to picturebox
Catch ex As Exception
End Try
End Sub
In mouse up event scale to get the correct result:
Private Sub pbZoneImage_MouseUp(sender As System.Object, e As System.Windows.Forms.MouseEventArgs) Handles pbZoneImage.MouseUp
Dim width, height As Integer
width = CInt(Math.Abs(mouse_Down.X - e.X) * (imgClone.Width / pbZoneImage.Width))
height = CInt(Math.Abs(mouse_Down.Y - e.Y) * (imgClone.Height / pbZoneImage.Height))
TextBox1.Text = width.ToString + " " + height.ToString
End Sub