Originally Posted by Teme64

I did a resizeable picture box as an user control some time ago. The picture box (= user control) maintains it's size, but you can zoom in and out the image with Zoom property.

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VB.NET Syntax (Toggle Plain Text)

Option Explicit On
Option Strict On
 
Imports System
Imports System.ComponentModel
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Windows.Forms
 
Public Class CPictureBox
 
  Inherits ScrollableControl
 
  '--------------------------------------------------------
  ' CPictureBox.vb
  '--------------------------------------------------------
 
  '--------------------------------------------------------
  ' CPictureBox Control
  '--------------------------------------------------------
 
  '--------------------------------------------------------
  ' Copyright © 2007-2008 xxx
  '
  ' Language: Visual Basic 2005.NET
  '
  ' Version: 1.0.0
  '
  ' Created: 10.12.2007 xxx
  '
  ' Modified: 29.4.2008 xxx
  '--------------------------------------------------------
 
  '--------------------------------------------------------
  ' Public data
  '--------------------------------------------------------
 
  '--------------------------------------------------------
  ' Private data
  '--------------------------------------------------------
 
  Private m_Image As Image
  Private m_Zoom As Single = 1.0F
  Private m_InterpolationMode As InterpolationMode = InterpolationMode.High
 
  '--------------------------------------------------------
  ' Private procedures
  '--------------------------------------------------------
 
  Private Sub InitComponent()
    '
    ' Init component
    '
 
    Try
      Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or ControlStyles.UserPaint Or ControlStyles.ResizeRedraw Or ControlStyles.UserPaint Or ControlStyles.DoubleBuffer, True)
      Me.AutoScroll = True
      'Me.BackColor = Color.White
      m_InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High
      m_Zoom = 1.0!
      m_Image = Nothing
    Catch ex As Exception
 
    End Try
 
  End Sub
 
  Private Sub UpdateScaleFactor()
    '
    ' Update scale factor
    '
 
    Try
      If m_Image Is Nothing Then
        Me.AutoScrollMargin = Me.Size
      Else
        Me.AutoScrollMinSize = New Size(CInt(Me.m_Image.Width * m_Zoom + 0.5F), CInt(Me.m_Image.Height * m_Zoom + 0.5F))
      End If
    Catch ex As Exception
 
    End Try
 
  End Sub
 
  '--------------------------------------------------------
  ' Event handlers
  '--------------------------------------------------------
 
  Public Sub New()
    '
    ' Initialize
    '
 
    Try
      InitComponent()
    Catch ex As Exception
 
    End Try
 
  End Sub
 
  Protected Overrides Sub Finalize()
    '
    ' Terminate control
    '
 
    Try
      MyBase.Finalize()
    Catch ex As Exception
 
    End Try
 
  End Sub
 
  Protected Overrides Sub OnPaintBackground(ByVal e As PaintEventArgs)
    '
    ' Do nothing
    '
 
    Try
      ' Do nothing
    Catch ex As Exception
 
    End Try
 
  End Sub
 
  Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
    '
    ' If no image, don't bother
    '
 
    Try
      If m_Image Is Nothing Then
        MyBase.OnPaintBackground(e)
        Exit Sub
      End If
      ' Set up a zoom matrix
      Dim mx As New Matrix(m_Zoom, 0, 0, m_Zoom, 0, 0)
      mx.Translate(Me.AutoScrollPosition.X / m_Zoom, Me.AutoScrollPosition.Y / m_Zoom)
      e.Graphics.Transform = mx
      e.Graphics.InterpolationMode = m_InterpolationMode
      e.Graphics.DrawImage(m_Image, New Rectangle(0, 0, Me.m_Image.Width, Me.m_Image.Height), 0, 0, m_Image.Width, m_Image.Height, GraphicsUnit.Pixel)
      MyBase.OnPaint(e)
    Catch ex As Exception
 
    End Try
 
  End Sub
 
  '--------------------------------------------------------
  ' Public procedures
  '--------------------------------------------------------
 
  ''' <summary>
  ''' Sets or gets the image in CPictureBox
  ''' </summary>
  ''' <value>Image</value>
  ''' <returns>Image</returns>
  ''' <remarks></remarks>
  Public Property Image() As Image
    '
    Get
      Return m_Image
    End Get
    Set(ByVal value As Image)
      m_Image = value
      If m_Image IsNot Nothing Then
        If m_Image.Height > 0 Then
          m_Zoom = CSng(Me.Height / m_Image.Height)
        Else
          m_Zoom = 1.0!
        End If
      End If
      UpdateScaleFactor()
      Invalidate()
    End Set
 
  End Property
 
  ''' <summary>
  ''' Sets or gets the zoom factor
  ''' </summary>
  ''' <value>Zoom factor</value>
  ''' <returns>Zoom factor</returns>
  ''' <remarks>Zoom factor should be between 0-5</remarks>
  Public Property Zoom() As Single
    '
    Get
      Return m_Zoom
    End Get
    Set(ByVal value As Single)
      If value < 0 OrElse value < 0.00001 Then
        value = 0.00001F
      End If
      m_Zoom = value
      UpdateScaleFactor()
      Invalidate()
    End Set
 
  End Property
 
  ''' <summary>
  ''' Sets or gets the interpolation mode used in the drawing
  ''' </summary>
  ''' <value>System.Drawing.Drawing2D.InterpolationMode</value>
  ''' <returns>System.Drawing.Drawing2D.InterpolationMode</returns>
  ''' <remarks></remarks>
  Public Property InterpolationMode() As InterpolationMode
    ' The interpolation mode used to smooth the drawing
    Get
      Return m_InterpolationMode
    End Get
    Set(ByVal value As InterpolationMode)
      m_InterpolationMode = value
    End Set
 
  End Property
 
End Class

Option Explicit On Option Strict On Imports System Imports System.ComponentModel Imports System.Drawing Imports System.Drawing.Drawing2D Imports System.Windows.Forms Public Class CPictureBox Inherits ScrollableControl '-------------------------------------------------------- ' CPictureBox.vb '-------------------------------------------------------- '-------------------------------------------------------- ' CPictureBox Control '-------------------------------------------------------- '-------------------------------------------------------- ' Copyright © 2007-2008 xxx ' ' Language: Visual Basic 2005.NET ' ' Version: 1.0.0 ' ' Created: 10.12.2007 xxx ' ' Modified: 29.4.2008 xxx '-------------------------------------------------------- '-------------------------------------------------------- ' Public data '-------------------------------------------------------- '-------------------------------------------------------- ' Private data '-------------------------------------------------------- Private m_Image As Image Private m_Zoom As Single = 1.0F Private m_InterpolationMode As InterpolationMode = InterpolationMode.High '-------------------------------------------------------- ' Private procedures '-------------------------------------------------------- Private Sub InitComponent() ' ' Init component ' Try Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or ControlStyles.UserPaint Or ControlStyles.ResizeRedraw Or ControlStyles.UserPaint Or ControlStyles.DoubleBuffer, True) Me.AutoScroll = True 'Me.BackColor = Color.White m_InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High m_Zoom = 1.0! m_Image = Nothing Catch ex As Exception End Try End Sub Private Sub UpdateScaleFactor() ' ' Update scale factor ' Try If m_Image Is Nothing Then Me.AutoScrollMargin = Me.Size Else Me.AutoScrollMinSize = New Size(CInt(Me.m_Image.Width * m_Zoom + 0.5F), CInt(Me.m_Image.Height * m_Zoom + 0.5F)) End If Catch ex As Exception End Try End Sub '-------------------------------------------------------- ' Event handlers '-------------------------------------------------------- Public Sub New() ' ' Initialize ' Try InitComponent() Catch ex As Exception End Try End Sub Protected Overrides Sub Finalize() ' ' Terminate control ' Try MyBase.Finalize() Catch ex As Exception End Try End Sub Protected Overrides Sub OnPaintBackground(ByVal e As PaintEventArgs) ' ' Do nothing ' Try ' Do nothing Catch ex As Exception End Try End Sub Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs) ' ' If no image, don't bother ' Try If m_Image Is Nothing Then MyBase.OnPaintBackground(e) Exit Sub End If ' Set up a zoom matrix Dim mx As New Matrix(m_Zoom, 0, 0, m_Zoom, 0, 0) mx.Translate(Me.AutoScrollPosition.X / m_Zoom, Me.AutoScrollPosition.Y / m_Zoom) e.Graphics.Transform = mx e.Graphics.InterpolationMode = m_InterpolationMode e.Graphics.DrawImage(m_Image, New Rectangle(0, 0, Me.m_Image.Width, Me.m_Image.Height), 0, 0, m_Image.Width, m_Image.Height, GraphicsUnit.Pixel) MyBase.OnPaint(e) Catch ex As Exception End Try End Sub '-------------------------------------------------------- ' Public procedures '-------------------------------------------------------- ''' <summary> ''' Sets or gets the image in CPictureBox ''' </summary> ''' <value>Image</value> ''' <returns>Image</returns> ''' <remarks></remarks> Public Property Image() As Image ' Get Return m_Image End Get Set(ByVal value As Image) m_Image = value If m_Image IsNot Nothing Then If m_Image.Height > 0 Then m_Zoom = CSng(Me.Height / m_Image.Height) Else m_Zoom = 1.0! End If End If UpdateScaleFactor() Invalidate() End Set End Property ''' <summary> ''' Sets or gets the zoom factor ''' </summary> ''' <value>Zoom factor</value> ''' <returns>Zoom factor</returns> ''' <remarks>Zoom factor should be between 0-5</remarks> Public Property Zoom() As Single ' Get Return m_Zoom End Get Set(ByVal value As Single) If value < 0 OrElse value < 0.00001 Then value = 0.00001F End If m_Zoom = value UpdateScaleFactor() Invalidate() End Set End Property ''' <summary> ''' Sets or gets the interpolation mode used in the drawing ''' </summary> ''' <value>System.Drawing.Drawing2D.InterpolationMode</value> ''' <returns>System.Drawing.Drawing2D.InterpolationMode</returns> ''' <remarks></remarks> Public Property InterpolationMode() As InterpolationMode ' The interpolation mode used to smooth the drawing Get Return m_InterpolationMode End Get Set(ByVal value As InterpolationMode) m_InterpolationMode = value End Set End Property End Class

Haven't used the control for a while and it surely misses features But I hope that the zooming functionality helps you.

The code was written with VB 2005 and VB 2008 may have some of the functionality "built-in".