CONTROLE IMAGE ZOOM/DÉZOOM

Imports System.Drawing.Drawing2D

Public Class ImageBox
    Inherits Control


    Private _image As Image
    Private _zoom As Single = 1
    Private _position As PointF = New PointF(0, 0)
    Private _width, _height, _rapportX, _rapportY As Single
    Private _DestRect, _SrcRect As Rectangle

    Private _LastPoint As Point

    Public Sub New()
        'pour eviter le scintillement
        Me.DoubleBuffered = True
    End Sub

    Public Sub New(ByVal pic As Image)
        'pour eviter le scintillement
        Me.DoubleBuffered = True

        Me.Image = pic
    End Sub

    Public Property Image() As Image
        Get
            Return _image
        End Get
        Set(ByVal value As Image)
            _image = value

            If _image IsNot Nothing AndAlso Me.Width <> 0 AndAlso Me.Height <> 0 Then
                _rapportX = (_image.Width / Me.Width)
                _rapportY = (_image.Height / Me.Height)
            End If

            draw_image(New PointF(0, 0))
        End Set
    End Property

    Private Sub draw_image(ByVal position As PointF, Optional ByVal delta As Single = 0)
        If _image IsNot Nothing Then
            _zoom -= delta / 100

            'Limite du zoom
            If _zoom > 1 Then
                _zoom += delta / 100
            ElseIf _zoom < 0 Then
                _zoom += delta / 100
            Else

                _width = _zoom * _image.Width
                _height = _zoom * _image.Height



                _position.X += (position.X - (position.X * (1 - (delta / 100)))) * _rapportX
                _position.Y += (position.Y - (position.Y * (1 - (delta / 100)))) * _rapportY

                '************ Vérification pour que l'image ne sorte pas du cadre **************
                If _position.X < 0 Then
                    _position.X = 0
                End If
                If _position.Y < 0 Then
                    _position.Y = 0
                End If

                If _position.Y + ((Me.Height * _rapportY)) * _zoom > _image.Height Then
                    _position.Y -= (_position.Y + ((Me.Height * _rapportY)) * _zoom) - _image.Height
                End If
                If _position.X + ((Me.Width * _rapportX)) * _zoom > _image.Width Then
                    _position.X -= (_position.X + ((Me.Width * _rapportX)) * _zoom) - _image.Width
                End If
                '*********************************************************************************

                _SrcRect = New Rectangle(_position.X, _position.Y, _width, _height)
            End If

        End If
        Me.Invalidate()
    End Sub

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        MyBase.OnPaint(e)
        If _image IsNot Nothing Then
            e.Graphics.DrawImage(_image, _DestRect, _SrcRect, GraphicsUnit.Pixel)
        Else
            e.Graphics.FillRectangle(Brushes.White, _DestRect)
            e.Graphics.DrawRectangle(Pens.Black, 0, 0, Me.Width - 1, Me.Height - 1)
        End If
    End Sub

    Protected Overrides Sub OnMouseWheel(ByVal e As System.Windows.Forms.MouseEventArgs)
        MyBase.OnMouseWheel(e)
        draw_image(e.Location, e.Delta / 30)
    End Sub


    Protected Overrides Sub OnMouseEnter(ByVal e As System.EventArgs)
        MyBase.OnMouseEnter(e)
        Me.Focus() 'l'évènement mousewheel ne fonctionne que lorsque le controle possède le focus
    End Sub

    Protected Overrides Sub OnMouseLeave(ByVal e As System.EventArgs)
        MyBase.OnMouseLeave(e)
        Me.Parent.Focus() 'on redonne le focus au controleur parent pour stopper les évènement mousewheel
    End Sub

    Protected Overrides Sub OnClientSizeChanged(ByVal e As System.EventArgs)
        MyBase.OnClientSizeChanged(e)
        _DestRect = New Rectangle(0, 0, Me.Width, Me.Height)
        If _image IsNot Nothing Then
            _rapportX = (_image.Width / Me.Width)
            _rapportY = (_image.Height / Me.Height)
        End If
    End Sub


    Protected Overrides Sub OnMouseDown(ByVal e As System.Windows.Forms.MouseEventArgs)
        MyBase.OnMouseDown(e)
        _LastPoint = e.Location
    End Sub

    Protected Overrides Sub OnMouseMove(ByVal e As System.Windows.Forms.MouseEventArgs)
        MyBase.OnMouseMove(e)
        If e.Button = Windows.Forms.MouseButtons.Left Then
            _position.X += ((_LastPoint.X - e.X) * _zoom) * _rapportX
            _position.Y += ((_LastPoint.Y - e.Y) * _zoom) * _rapportY

            draw_image(New PointF(0, 0))

            _LastPoint = e.Location
        End If
    End Sub

    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        MyBase.Dispose(disposing)
        If _image IsNot Nothing Then
            _image.Dispose()
        End If
    End Sub
End Class