Basic Pixel Operations in vb.net

''Author: Andrew Buckau
''Date: Sep. 23, 2013

'''WinAPi Class File'''
Public Class WinApi
#Region "API Declarations"
    'Public Declare Function GetWindowRect Lib "user32.dll" (ByVal hWnd As IntPtr, ByRef lpRect As Rect) As Boolean
    Public Declare Function GetClientRect Lib "user32.dll" (ByVal hWnd As IntPtr, ByRef lpRect As Rect) As Boolean
    Public Declare Function GetDesktopWindow Lib "user32" () As IntPtr
    Public Declare Function GetPixel Lib "gdi32" (ByVal hDC As IntPtr, ByVal x As Integer, ByVal y As Integer) As Integer
    Public Declare Function GetWindowDC Lib "user32" (ByVal hWnd As IntPtr) As IntPtr
    Public Declare Function ReleaseDC Lib "user32" (ByVal hWnd As IntPtr, ByVal hDC As IntPtr) As Integer
    Public Declare Function ClientToScreen Lib "user32.dll" (ByVal hWnd As IntPtr, ByRef lpPoint As Point) As Boolean
    'Public Declare Function GetForegroundWindow Lib "user32.dll" () As IntPtr

#End Region
#Region "Structs"
    Public Structure Rect
        ''NOT compatible with System.Drawing.Rectangle. Items are declared differently | different order.
        Dim Left As Int32
        Dim Top As Int32
        Dim Right As Int32
        Dim Bottom As Int32
        Public ReadOnly Property Width As Int32
            Get
                Return Right - Left
            End Get
        End Property
        Public ReadOnly Property Height As Int32
            Get
                Return Bottom - Top
            End Get
        End Property
    End Structure
#End Region
End Class

''' END WinAPi File ''''''''''''''''''''''''''''''''
''''''''''''''''''''''''''''''''''''''''''''''''''''
'''ScreenManager Class FIle'''''''''''''''''''''''''
Public Class ScreenManager
    ''' <summary>
    ''' Gets the color of a single pixel and returns as a Color.
    ''' </summary>
    Public Shared Function GetPixel(ByVal x As Int32, ByVal y As Int32) As Color
        Dim hWnd As IntPtr = WinApi.GetDesktopWindow()
        Dim hDC As IntPtr = WinApi.GetWindowDC(hWnd)
        Dim lColor As Int32 = WinApi.GetPixel(hDC, x, y)
        WinApi.ReleaseDC(hWnd, hDC)
        Return ColorTranslator.FromWin32(lColor) '<--nice converter function : Color struct is BIG :/ 20 something bytes.
    End Function

    ''' <summary>
    ''' Takes a screenshot of the screen and returns as a Bitmap.
    ''' </summary>
    ''' <param name="tl">Top-Left point of the region to copy</param>
    ''' <param name="width">Width of the region to copy</param>
    ''' <param name="height">Height of the region to copy</param>
    Public Shared Function GetScreenArea(ByVal tl As Point, ByVal width As Int32, ByVal height As Int32) As Bitmap
        Dim _rtnBmp As New Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format24bppRgb)
        Dim _gr As Graphics = Graphics.FromImage(_rtnBmp)
        _gr.CopyFromScreen(tl, New Point(0, 0), New System.Drawing.Size(width, height), CopyPixelOperation.SourceCopy)
        _gr.Dispose()
        Return _rtnBmp
    End Function

    ''' <summary>
    ''' Returns a WinApi.Rect (left,top,right,bottom) for the given window's client area. Does Not include Form Borders.
    ''' </summary>
    ''' <param name="hWnd">Handle to the window</param>
    Public Shared Function GetWindowClientRect(ByVal hWnd As IntPtr) As WinApi.Rect
        Dim _rtnRect As New WinApi.Rect
        Dim _tl As New Point(0, 0)
        WinApi.GetClientRect(hWnd, _rtnRect) '' only fills  Right and Bottom --> is Width and Height.
        WinApi.ClientToScreen(hWnd, _tl)
        _rtnRect.Top = _tl.Y
        _rtnRect.Left = _tl.X
        _rtnRect.Right += _rtnRect.Left
        _rtnRect.Bottom += _rtnRect.Top
        Return _rtnRect
    End Function

    ''' <summary>
    ''' Scans through a bitmap for 1 specific color
    ''' </summary>
    ''' <param name="aBitmap">The bitmap to be searched.</param>
    ''' <param name="searchColor">The color to search for.</param>
    Public Shared Function FindColorLocations(ByRef aBitmap As Bitmap, ByVal searchColor As Color) As Point()
        Dim _rtnPts As New List(Of Point)
        Dim _tmpColor As New Color
        For xx As Int32 = 0 To aBitmap.Width - 1
            For yy As Int32 = 0 To aBitmap.Height - 1
                _tmpColor = aBitmap.GetPixel(xx, yy)
                If _tmpColor.R = searchColor.R And _tmpColor.G = searchColor.G And _tmpColor.B = searchColor.B Then
                    _rtnPts.Add(New Point(xx, yy)) ''image's pixel-color matched searchColor. Add x,y to the list.
                End If
            Next
        Next
        If _rtnPts.Count = 0 Then
            _rtnPts.Add(New Point(-1, -1)) '' FAILURE. No points found.
        End If
        Return _rtnPts.ToArray()
    End Function

End Class

'''END ScreenManager file'''''
''''''''''''''''''''''''''''''
''' Form1 demo of use'''''''''
Public Class Form1
    Private _ss As Bitmap '' Screenshot image
    Private _searchColor As Color = Color.FromArgb(255, 0, 0) '' Search Color. Defaulted to pure red.


    Private Sub cmdTakeSS_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdTakeSS.Click
        _ss = ScreenManager.GetScreenArea(New Point(0, 0), Screen.PrimaryScreen.WorkingArea.Width, Screen.PrimaryScreen.WorkingArea.Height)
        pbxSS.Image = _ss
        pbxSS.Refresh()
    End Sub

    Private Sub cmdSetSearchColor_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSetSearchColor.Click
        _searchColor = ScreenManager.GetPixel(Cursor.Position.X, Cursor.Position.Y)
        Panel1.BackColor = _searchColor
        Panel1.Refresh()
    End Sub

    Private Sub cmdFindColor_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdFindColor.Click
        Dim _foundPoints() As Point = ScreenManager.FindColorLocations(_ss, _searchColor)

        If _foundPoints(0).X = -1 Then
            ''fail. todo: add proper documentation. FindColorLocations() returns a single point of (-1,-1) on failure.
            MessageBox.Show("No points found of that color.")
        Else
            Dim _outStr As New System.Text.StringBuilder

            For Each pp As Point In _foundPoints
                _outStr.Append(pp.ToString & "  ") '' displays as {X,Y}
            Next
            MessageBox.Show(_foundPoints.Length & " points found. " & Environment.NewLine _
                        & _outStr.ToString)
        End If
    End Sub
End Class
'''END of Form1 file