VB.Net - Simple Proper Image Scaling in Correct Aspect Ratio

First Submission to the CodeBank!

While I was working on a program I found the need to display pictures, and (since I'm OCD) I needed them to be the correct aspect ratio. This sounds (and is) quite simple, but sometimes things get over complicated. It actually took me a few tries to figure this out, but what I ended up with was a Very Simple, Extremely Portable Function which can scale any System.Drawing.Image to any Target Size.
While I was working on it, I did multiple searches for simmilar code, but what I found was usually WAY over complicated, or only scaled down. I'm Submitting this after searching the CodeBank and not finding anything resembling a scaling snippet. I'm hoping other people can benefit from the simplicity of this.

Forgive me for not commenting, I believe it too simple to require comments (they just get in the way without saying anything about it).
Modified by Suggestion of boops boops. Credit where due.

VB.Net Code:

Public Function ScaleImage(ByVal OldImage As Image, ByVal TargetHeight As Integer,_
                           ByVal TargetWidth As Integer) As System.Drawing.Image
 
        Dim NewHeight As Integer = TargetHeight
        Dim NewWidth As Integer = NewHeight / OldImage.Height * OldImage.Width
 
        If NewWidth > TargetWidth Then
            NewWidth = TargetWidth
            NewHeight = NewWidth / OldImage.Width * OldImage.Height
        End If
 
        Return New Bitmap(OldImage, NewWidth, NewHeight)
 
End Function

Example Usage:

VB.Net Code:

Picturebox1.Image = ScaleImage(Image.Fromfile(Picture.png),_
                               Picturebox1.Height, Picturebox1.Width)

Note: Set the Picturebox's SizeMode to CenterImage

Hi stepdragon,

Congratulations on your first CodeBank contribution. That's a function that a lot of people should find useful.

It's neat but you could make the second half even neater. I would replace the lines from 12 onwards by this:

Code:

---

Return New Bitmap(Old Image, NewWidth, NewHeight)

---

That automatically scales the old image to the new size.

BB

I knew I saw a better way of doing that somewhere (I couldn't remember how to do that, so I used another code snippet) now it'll truly be fool-proof as everything is easy to read. I'll amend it right now.

I made something similar ages ago:

vb Code:

Public Enum BestFitStyle
            Zoom
            Stretch
        End Enum
 
        Public Function GetBestFitRect(ByVal rectFrame As RectangleF, ByVal rect As RectangleF, Optional ByVal BestFitStyle As BestFitStyle = BestFitStyle.Zoom) As RectangleF
            Dim origImageRatio = rect.Width / rect.Height
            Dim canvasRatio = rectFrame.Width / rectFrame.Height
            Dim DrawRect As RectangleF
            If (origImageRatio > canvasRatio AndAlso BestFitStyle = Images.BestFitStyle.Stretch) OrElse (origImageRatio < canvasRatio AndAlso BestFitStyle = Images.BestFitStyle.Zoom) Then
                DrawRect = New RectangleF(rectFrame.Left, rectFrame.Top, rectFrame.Width, rectFrame.Width * (1 / origImageRatio))
            Else
                DrawRect = New RectangleF(rectFrame.Left, rectFrame.Top, rectFrame.Height * origImageRatio, rectFrame.Height)
            End If
            DrawRect.X += ((rectFrame.Width - DrawRect.Width) / 2)
            DrawRect.Y += ((rectFrame.Height - DrawRect.Height) / 2)
            Return DrawRect
        End Function
 
        Public Sub DrawImageBestFit(ByVal g As Graphics, ByVal rect As RectangleF, ByVal image As Image, Optional ByVal BestFitStyle As BestFitStyle = BestFitStyle.Zoom)
            Dim oldRegion = g.Clip.Clone
            g.SetClip(rect, CombineMode.Intersect)
            Dim DrawRect = GetBestFitRect(rect, New RectangleF(0, 0, image.Width, image.Height))
            g.DrawImage(image, DrawRect)
            g.Clip = oldRegion
        End Sub

... Supports zoom and stretch (keping aspect) types
...draws the scaled image directly on the new graphics.

Kris

I was going to add some extra features to my code, but I have since decided against it. I like the simplicity of my code and how it is a useful way to properly display programs for programmers who don't work with graphics and want a simple easy and effective code snippet. If I make the code less simple to accomodate middle level programming needs, then I'm probably going to both not make it effective enough for the power user, and make it too complicated for the entry level user. Therefore I've decided to leave the code as is so that people who don't want to fuss with graphics can display images properly without thinking about it.