Make .NET snipping tool compatible with multiple monitors

Question

An alternative snipping tool solution was provided in this posting: .NET Equivalent of Snipping Tool

Now it's necessary to make it work for selected screens (on multi-monitor systems).

The code has been modified accordingly:

Public Class SnippingTool


    Private Shared _Screen As Screen

    Private Shared BitmapSize As Size

    Private Shared Graph As Graphics


    Public Shared Function Snip(ByVal screen As Screen) As Image

        _Screen = screen

        Dim bmp As New Bitmap(screen.Bounds.Width, screen.Bounds.Height, System.Drawing.Imaging.PixelFormat.Format32bppPArgb)

        Dim gr As Graphics = Graphics.FromImage(bmp)

        Graph = gr


        gr.SmoothingMode = Drawing2D.SmoothingMode.None '###

        BitmapSize = bmp.Size


        Using snipper = New SnippingTool(bmp)

            snipper.Location = New Point(screen.Bounds.Left, screen.Bounds.Top)

            If snipper.ShowDialog() = DialogResult.OK Then
                Return snipper.Image
            End If

        End Using

        Return Nothing


    End Function



    Public Sub New(ByVal screenShot As Image)
        InitializeComponent()
        Me.BackgroundImage = screenShot
        Me.ShowInTaskbar = False
        Me.FormBorderStyle = FormBorderStyle.None


        'Me.WindowState = FormWindowState.Maximized

        Me.DoubleBuffered = True
    End Sub
    Public Property Image() As Image
        Get
            Return m_Image
        End Get
        Set(ByVal value As Image)
            m_Image = Value
        End Set
    End Property
    Private m_Image As Image


    Private rcSelect As New Rectangle()
    Private pntStart As Point

    Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
        ' Start the snip on mouse down
        If e.Button <> MouseButtons.Left Then
            Return
        End If
        pntStart = e.Location
        rcSelect = New Rectangle(e.Location, New Size(0, 0))
        Me.Invalidate()
    End Sub
    Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)
        ' Modify the selection on mouse move
        If e.Button <> MouseButtons.Left Then
            Return
        End If
        Dim x1 As Integer = Math.Min(e.X, pntStart.X)
        Dim y1 As Integer = Math.Min(e.Y, pntStart.Y)
        Dim x2 As Integer = Math.Max(e.X, pntStart.X)
        Dim y2 As Integer = Math.Max(e.Y, pntStart.Y)
        rcSelect = New Rectangle(x1, y1, x2 - x1, y2 - y1)
        Me.Invalidate()
    End Sub


    Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
        ' Complete the snip on mouse-up
        If rcSelect.Width <= 0 OrElse rcSelect.Height <= 0 Then
            Return
        End If
        Image = New Bitmap(rcSelect.Width, rcSelect.Height)
        Using gr As Graphics = Graphics.FromImage(Image)
            gr.DrawImage(Me.BackgroundImage, New Rectangle(0, 0, Image.Width, Image.Height), rcSelect, GraphicsUnit.Pixel)
        End Using
        DialogResult = DialogResult.OK
    End Sub
    Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
        ' Draw the current selection
        Using br As Brush = New SolidBrush(Color.FromArgb(120, Color.White))
            Dim x1 As Integer = rcSelect.X
            Dim x2 As Integer = rcSelect.X + rcSelect.Width
            Dim y1 As Integer = rcSelect.Y
            Dim y2 As Integer = rcSelect.Y + rcSelect.Height
            e.Graphics.FillRectangle(br, New Rectangle(0, 0, x1, Me.Height))
            e.Graphics.FillRectangle(br, New Rectangle(x2, 0, Me.Width - x2, Me.Height))
            e.Graphics.FillRectangle(br, New Rectangle(x1, 0, x2 - x1, y1))
            e.Graphics.FillRectangle(br, New Rectangle(x1, y2, x2 - x1, Me.Height - y2))
        End Using
        Using pen As New Pen(Color.Red, 3)
            e.Graphics.DrawRectangle(pen, rcSelect)
        End Using
    End Sub
    Protected Overrides Function ProcessCmdKey(ByRef msg As Message, ByVal keyData As Keys) As Boolean
        ' Allow canceling the snip with the Escape key
        If keyData = Keys.Escape Then
            Me.DialogResult = DialogResult.Cancel
        End If
        Return MyBase.ProcessCmdKey(msg, keyData)
    End Function

    Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
        MyBase.OnLoad(e)
        Me.Size = New Size(_Screen.Bounds.Width, _Screen.Bounds.Height)
        Dim area = _Screen.WorkingArea
        Graph.CopyFromScreen(area.X, area.Y, area.Y, area.Y, BitmapSize)
    End Sub

End Class

But it refuses to work as expected. The snipper doesn't appear on the selected screen, instead it appears on the first one, regardless of the "screen" parameter in "Snip" function. How to make it work correctly?

UPDATE: The latest snipper version appears on correct screen, but blank.

UPDATE X2 : The code above has been updated to reflect the latest version, which now works properly.

Answer 1

LoveDotNet, I believe there is a small problem with your source code, the following line:

Graph.CopyFromScreen(area.X, area.Y, area.Y, area.Y, BitmapSize)

Should be:

Graph.CopyFromScreen(area.X, area.Y, 0, 0, BitmapSize)

Also, just a quick tip to anyone who wants to use this code you can invoke it like the following:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim img As Image = SnippingTool.Snip(Screen.AllScreens(0)) 'Set to (1) for secondary monitor'
End Sub

Also, when you create your SnippingTool form, be sure to change the StartPosition property to Manual.

Big Edit:

I did some work to support multiple monitors at once, which doesn't require the developer to select which monitor to use (this clones the "Snipping Tool" a little closer).

Basically I'm iterating through all of the screens to find the minimum X and Y coordinates, and the largest Right and Bottom, this lets us evaluate the full size of the "Virtual Monitor":

I've tested it with my configuration which is:

Primary 1280x800

Secondary 1280x1024 w/ -224 X offset

Code:

'SnippingTool Code: Place this in a new form (set the StartUp Property to Manual)'
Public Class SnippingTool


Private Shared _Screen As Screen

Private Shared BitmapSize As Size

Private Shared Graph As Graphics

Private Structure MultiScreenSize
    Dim minX As Integer
    Dim minY As Integer
    Dim maxRight As Integer
    Dim maxBottom As Integer
End Structure


Private Shared Function FindMultiScreenSize() As MultiScreenSize

    Dim minX As Integer = Screen.AllScreens(0).Bounds.X
    Dim minY As Integer = Screen.AllScreens(0).Bounds.Y

    Dim maxRight As Integer = Screen.AllScreens(0).Bounds.Right
    Dim maxBottom As Integer = Screen.AllScreens(0).Bounds.Bottom

    For Each aScreen As Screen In Screen.AllScreens
        If aScreen.Bounds.X < minX Then
            minX = aScreen.Bounds.X
        End If

        If aScreen.Bounds.Y < minY Then
            minY = aScreen.Bounds.Y
        End If

        If aScreen.Bounds.Right > maxRight Then
            maxRight = aScreen.Bounds.Right
        End If

        If aScreen.Bounds.Bottom > maxBottom Then
            maxBottom = aScreen.Bounds.Bottom
        End If
    Next
    Dim m_MultiScreenSize As MultiScreenSize
    With m_MultiScreenSize
        .minX = minX
        .minY = minY
        .maxBottom = maxBottom
        .maxRight = maxRight
    End With
    Return m_MultiScreenSize
End Function
Public Shared Function Snip() As Image
    Dim m_MultiScreenSize As MultiScreenSize = FindMultiScreenSize()

    Dim bmp As New Bitmap(m_MultiScreenSize.maxRight - m_MultiScreenSize.minX, _
                          m_MultiScreenSize.maxBottom - m_MultiScreenSize.minY, _
                          System.Drawing.Imaging.PixelFormat.Format32bppPArgb)
    Dim gr As Graphics = Graphics.FromImage(bmp)

    Graph = gr


    gr.SmoothingMode = Drawing2D.SmoothingMode.None 
    BitmapSize = bmp.Size


    Using snipper = New SnippingTool(bmp)

        snipper.Location = New Point(m_MultiScreenSize.minX, m_MultiScreenSize.minY)

        If snipper.ShowDialog() = DialogResult.OK Then
            Return snipper.Image
        End If

    End Using

    Return Nothing


End Function



Public Sub New(ByVal screenShot As Image)
    InitializeComponent()
    Me.BackgroundImage = screenShot
    Me.ShowInTaskbar = False
    Me.FormBorderStyle = FormBorderStyle.None

    Me.DoubleBuffered = True
End Sub
Public Property Image() As Image
    Get
        Return m_Image
    End Get
    Set(ByVal value As Image)
        m_Image = Value
    End Set
End Property
Private m_Image As Image


Private rcSelect As New Rectangle()
Private pntStart As Point

Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs)
    ' Start the snip on mouse down'
    If e.Button <> MouseButtons.Left Then
        Return
    End If
    pntStart = e.Location
    rcSelect = New Rectangle(e.Location, New Size(0, 0))
    Me.Invalidate()
End Sub
Protected Overrides Sub OnMouseMove(ByVal e As MouseEventArgs)
    ' Modify the selection on mouse move'
    If e.Button <> MouseButtons.Left Then
        Return
    End If
    Dim x1 As Integer = Math.Min(e.X, pntStart.X)
    Dim y1 As Integer = Math.Min(e.Y, pntStart.Y)
    Dim x2 As Integer = Math.Max(e.X, pntStart.X)
    Dim y2 As Integer = Math.Max(e.Y, pntStart.Y)
    rcSelect = New Rectangle(x1, y1, x2 - x1, y2 - y1)
    Me.Invalidate()
End Sub


Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs)
    ' Complete the snip on mouse-up'
    If rcSelect.Width <= 0 OrElse rcSelect.Height <= 0 Then
        Return
    End If
    Image = New Bitmap(rcSelect.Width, rcSelect.Height)
    Using gr As Graphics = Graphics.FromImage(Image)
        gr.DrawImage(Me.BackgroundImage, New Rectangle(0, 0, Image.Width, Image.Height), _
                     rcSelect, GraphicsUnit.Pixel)
    End Using
    DialogResult = DialogResult.OK
End Sub
Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)
    ' Draw the current selection'
    Using br As Brush = New SolidBrush(Color.FromArgb(120, Color.White))
        Dim x1 As Integer = rcSelect.X
        Dim x2 As Integer = rcSelect.X + rcSelect.Width
        Dim y1 As Integer = rcSelect.Y
        Dim y2 As Integer = rcSelect.Y + rcSelect.Height
        e.Graphics.FillRectangle(br, New Rectangle(0, 0, x1, Me.Height))
        e.Graphics.FillRectangle(br, New Rectangle(x2, 0, Me.Width - x2, Me.Height))
        e.Graphics.FillRectangle(br, New Rectangle(x1, 0, x2 - x1, y1))
        e.Graphics.FillRectangle(br, New Rectangle(x1, y2, x2 - x1, Me.Height - y2))
    End Using
    Using pen As New Pen(Color.Red, 3)
        e.Graphics.DrawRectangle(pen, rcSelect)
    End Using
End Sub
Protected Overrides Function ProcessCmdKey(ByRef msg As Message, ByVal keyData As Keys) As Boolean
    ' Allow canceling the snip with the Escape key'
    If keyData = Keys.Escape Then
        Me.DialogResult = DialogResult.Cancel
    End If
    Return MyBase.ProcessCmdKey(msg, keyData)
End Function

Protected Overrides Sub OnLoad(ByVal e As System.EventArgs)
    MyBase.OnLoad(e)
    Dim m_MultiScreenSize As MultiScreenSize = FindMultiScreenSize()
    Me.Size = New Size(m_MultiScreenSize.maxRight - m_MultiScreenSize.minX, _
                       m_MultiScreenSize.maxBottom - m_MultiScreenSize.minY)

    Graph.CopyFromScreen(m_MultiScreenSize.minX, m_MultiScreenSize.minY, 0, 0, BitmapSize)
End Sub
 End Class

And you can call it like this:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim img As Image = SnippingTool.Snip()
    img.Save("C:\ScreenShot.png")
End Sub