Picturebox - Get image inside drawn rectangle and show in another Picturebox

问题

I made a search and successfully found a solution to draw a rectangle inside my Picturebox while mousemoving using a class named Rectangulo:

Public Class Form1

    Dim SelectionBoxObj As New Rectangulo()
    Dim IsMouseDown As Boolean = False
    Public SelectedObjPoint As Point

    Private Sub PictureBox1_MouseDown(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            IsMouseDown = True
            SelectedObjPoint = New Point(e.X, e.Y)
        End If
    End Sub

    Private Sub PictureBox1_MouseMove(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove

        If IsMouseDown = True Then
            If e.X < SelectionBoxObj.X Then
                SelectionBoxObj.X = e.X
                SelectionBoxObj.Width = SelectedObjPoint.X - e.X
            Else
                SelectionBoxObj.X = SelectedObjPoint.X
                SelectionBoxObj.Width = e.X - SelectedObjPoint.X

            End If
            If e.Y < SelectedObjPoint.Y Then
                SelectionBoxObj.Y = e.Y
                SelectionBoxObj.Height = SelectedObjPoint.Y - e.Y
            Else
                SelectionBoxObj.Y = SelectedObjPoint.Y
                SelectionBoxObj.Height = e.Y - SelectedObjPoint.Y
            End If

            Me.Refresh()
        End If

    End Sub

    Private Sub PictureBox1_MouseUp(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        IsMouseDown = False
    End Sub

    Private Sub PictureBox1_Paint(sender As Object, e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        If SelectionBoxObj.Width > 0 And SelectionBoxObj.Height > 0 Then
            Dim oGradientBrush As Brush = New Drawing.Drawing2D.LinearGradientBrush(SelectionBoxObj.RectangleF, SelectionBoxObj.FillColor, SelectionBoxObj.FillColor, Drawing.Drawing2D.LinearGradientMode.Vertical)
            e.Graphics.FillRectangle(oGradientBrush, SelectionBoxObj.RectangleF)

            Dim TempPen = New Pen(SelectionBoxObj.BorderLineColor, SelectionBoxObj.BorderLineWidth)
            TempPen.DashStyle = SelectionBoxObj.BorderLineType
            e.Graphics.DrawRectangle(TempPen, SelectionBoxObj.RectangleF.X, SelectionBoxObj.RectangleF.Y, SelectionBoxObj.RectangleF.Width, SelectionBoxObj.RectangleF.Height)
        End If
    End Sub
End Class

And the Rectangle Class code:

    Public Class Rectangulo
    Private m_BorderLineColor As Color = Drawing.Color.FromArgb(255, 51, 153, 255)
    Private m_FillColor As Color = Drawing.Color.FromArgb(40, 51, 153, 255)
    Private m_BorderLineType As Drawing2D.DashStyle = Drawing2D.DashStyle.Solid
    Private m_BorderLineWidth As Integer = 1
    Private m_X As Single
    Private m_Y As Single
    Private m_Width As Single
    Private m_Height As Single
    Private m_RectangleF As RectangleF

    Public Property BorderLineWidth() As Integer
        Get
            Return m_BorderLineWidth
        End Get
        Set(ByVal value As Integer)
            m_BorderLineWidth = value
        End Set
    End Property
    Public Property BorderLineType() As Drawing2D.DashStyle
        Get
            Return m_BorderLineType
        End Get
        Set(ByVal value As Drawing2D.DashStyle)
            m_BorderLineType = value
        End Set
    End Property
    Public Property BorderLineColor() As Color
        Get
            Return m_BorderLineColor
        End Get
        Set(ByVal value As Color)
            m_BorderLineColor = value
        End Set
    End Property
    Public Property FillColor() As Color
        Get
            Return m_FillColor
        End Get
        Set(ByVal value As Color)
            m_FillColor = value
        End Set
    End Property
    Public Property X() As Single
        Get
            Return m_RectangleF.X
        End Get
        Set(ByVal value As Single)
            m_RectangleF.X = value
        End Set
    End Property
    Public Property Y() As Single
        Get
            Return m_RectangleF.Y
        End Get
        Set(ByVal value As Single)
            m_RectangleF.Y = value
        End Set
    End Property
    Public Property Width() As Single
        Get
            Return m_RectangleF.Width
        End Get
        Set(ByVal value As Single)
            m_RectangleF.Width = value
        End Set
    End Property
    Public Property Height() As Single
        Get
            Return m_RectangleF.Height
        End Get
        Set(ByVal value As Single)
            m_RectangleF.Height = value
        End Set
    End Property
    Public Property RectangleF() As RectangleF
        Get
            Return m_RectangleF
        End Get
        Set(ByVal value As RectangleF)
            m_RectangleF = value
        End Set
    End Property
End Class

So far I found this article and adjusted with my code in mousemove event like this:

Dim top As Integer = Integer.Parse(SelectionBoxObj.Y)
        Dim left As Integer = Integer.Parse(SelectionBoxObj.X)
        Dim width As Integer = Integer.Parse(SelectionBoxObj.Width)
        Dim height As Integer = Integer.Parse(SelectionBoxObj.Height)

        ' Make a Bitmap to hold the result.
        If width > 0 And height > 0 Then
            Dim bm As New Bitmap(width, height)

            ' Associate a Graphics object with the Bitmap
            Using gr As Graphics = Graphics.FromImage(bm)
                ' Define source and destination rectangles.
                Dim src_rect As New Rectangle(left, top, width, _
                    height)
                Dim dst_rect As New Rectangle(0, 0, width, height)

                ' Copy that part of the image.
                gr.DrawImage(PictureBox1.Image, dst_rect, src_rect, _
                    GraphicsUnit.Pixel)
            End Using

            ' Display the result.
            PictureBox2.Image = bm

And It's almost done! But the only problem now is the points are incorrect, the image displayed is always from the middle of selection to right and not his full size of selection

Thanks in advance

来源：https://stackoverflow.com/questions/16418145/picturebox-get-image-inside-drawn-rectangle-and-show-in-another-picturebox