FAQ: How do I resize an image by the same scale?

Question

How do I resize an image by the same scale?

---

Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Answer 1

The main idea: Create a new Bitmap with a new size, then draw the original Bitmap on the new Bitmap object.

Prerequisites: Drag&drop Button1, PictureBox1 and PictureBox2 onto Form1.

 

Public Class Form1
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        PictureBox1.ImageLocation = "D:\mm.jpg"
        PictureBox2.ImageLocation = "D:\mmm.jpg"
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        resizeImage(PictureBox1.ImageLocation, PictureBox1)
        resizeImage(PictureBox2.ImageLocation, PictureBox2)
    End Sub

    Public Sub resizeImage(ByVal imgPath As String, ByVal picbox As PictureBox)
        ' Get the source bitmap   
        Dim bm_source As Bitmap = New Bitmap(imgPath)
        ' Record the scale of source bitmap   
        Dim scale As Double = bm_source.Height / bm_source.Width
        ' Make a new bitmap   
        Dim bm_dest As New Bitmap(CInt(picbox.Width), CInt(picbox.Width * scale))
        ' Make a Graphics object for the new Bitmap.   
        Dim gr_dest As Graphics = Graphics.FromImage(bm_dest)
        ' Copy the source image into the destination bitmap   
        gr_dest.DrawImage(bm_source, 0, 0, bm_dest.Width + 1, bm_dest.Height + 1)
        ' Display the new bitmap in PictureBox   
        picbox.Image = bm_dest
    End Sub
End Class

 

Related thread:

http://social.msdn.microsoft.com/forums/en-US/vbide/thread/69bae6d7-eb4e-49cd-b078-704a028e9318

 

For more FAQ about Visual Basic .NET General, please see Visual Basic .NET General FAQ

---

Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

Answer 2

Additionally, here is one better approach to zoom image in PictureBox by scrolling mouse wheel.

Prerequisites: Drag&drop PictureBox1 onto Form1.

Public Class Form1     Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load         PictureBox1.SizeMode = PictureBoxSizeMode.Zoom         PictureBox1.ImageLocation = "D:\1.jpg"     End Sub       Private Sub PictureBox1_MouseWheel(ByVal sender As System.Object, ByVal e As MouseEventArgs) Handles PictureBox1.MouseWheel         If e.Delta <> 0 Then             If e.Delta <= 0 Then                 If PictureBox1.Width < 50 Then Exit Sub 'minimum 50?             Else                 If PictureBox1.Width > 500 Then Exit Sub 'maximum 500?             End If             PictureBox1.Width += CInt(PictureBox1.Width * e.Delta / 1000)             PictureBox1.Height += CInt(PictureBox1.Height * e.Delta / 1000)         End If     End Sub       Private Sub PictureBox1_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove         PictureBox1.Select()     End Sub   End Class

Trackback: http://social.msdn.microsoft.com/Forums/en-US/vblanguage/thread/50d2ad98-405e-4943-a300-021fd3ecbaa4

---

Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.
Send us any feedback you have about the help from MSFT at [e-mail].