pinvoke.net: Edit: gdi32.GetPixel

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Summary: The GetPixel API

!!!!C# Signature:
 [DllImport("gdi32.dll")]
 static extern uint GetPixel(IntPtr hdc, int nXPos, int nYPos);
!!!!VB.NET Signature
 <DllImport("gdi32.dll", SetLastError:=True)> _
 Public Function GetPixel(hdc As IntPtr, _
                          nXPos As Integer, _
                          nYPos as Integer) As UInteger
 End Function

!!!!VB Signature:
 Public Declare Function GetPixel Lib "gdi32" Alias "GetPixel" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long) As Long
!!!!User-Defined Types:
None.
!!!!Alternative Managed API:
static Color GetColor(int x, int y)
{
    using (Bitmap bmp = new Bitmap(Screen.PrimaryScreen.Bounds.Width,
                                   Screen.PrimaryScreen.Bounds.Height, 
                                   PixelFormat.Format32bppArgb)) 
    {
        using (Graphics g = Graphics.FromImage(bmp)) 
        {
            g.CopyFromScreen(Screen.PrimaryScreen.Bounds.X,
                             Screen.PrimaryScreen.Bounds.Y, 
                             0, 0, 
                             Screen.PrimaryScreen.Bounds.Size, 
                             CopyPixelOperation.SourceCopy);
        }
        return bmp.GetPixel(x, y);
    }
}
//To get colors in ARGB format use color.A, color.R, color.G and color.B
//Example:
Color color = GetColor(960, 540);
byte alpha = color.A;
byte red   = color.R;
byte green = color.G;
byte blue  = color.B;
!!!!Notes:
None

!!!!Tips & Tricks:
Please add some!

!!!!Sample Code:
  [DllImport("user32.dll")]
  static extern IntPtr GetDC(IntPtr hwnd);

[DllImport("user32.dll")]
  static extern Int32 ReleaseDC(IntPtr hwnd, IntPtr hdc);

[DllImport("gdi32.dll")]
  static extern uint GetPixel(IntPtr hdc,int nXPos,int nYPos);

// Print out the RGB value of the pixel which is under the mouse cursor.
  // NB: BLUE and RED components will be swapped because GetPixel returns ABGR
  static private void myControl_MouseMove(object sender,System.Windows.Forms.MouseEventArgs e)
  {
    IntPtr hdc = GetDC(IntPtr.Zero);
    uint pixel = GetPixel(hdc, Cursor.Position.X, Cursor.Position.Y);
    ReleaseDC(IntPtr.Zero,hdc);
    Color color = Color.FromArgb((int)pixel);
    Console.WriteLine("Color is {0}",color);
  }

!!!!2nd Example (above did not work for me, here is my solution):
        [DllImport("gdi32.dll")]
        static extern IntPtr CreateDC(string strDriver,
          string strDevice, string strOutput, IntPtr pData);

[DllImport("gdi32.dll")]
        static extern bool DeleteDC(IntPtr hdc);

[DllImport("gdi32.dll")]
        static extern int GetPixel(IntPtr hdc, int nXPos, int nYPos);

// ...
	IntPtr hdcScreen = CreateDC("Display", null, null, IntPtr.Zero);
	int cr = GetPixel(hdcScreen, x, y);
	Color color = Color.FromArgb((cr & 0x000000FF),
		(cr & 0x0000FF00) >> 8,
		(cr & 0x00FF0000) >> 16);
	DeleteDC(hdcScreen);
	// ... and apply the color to Bitmap-struct via SetPixel() or whatever else you want to do with it..
	
!!!!Wrapper Class
  using System;
  using System.Drawing;
  using System.Runtime.InteropServices;

sealed class Win32
  {
      [DllImport("user32.dll")]
      static extern IntPtr GetDC(IntPtr hwnd);
  
      [DllImport("user32.dll")]
      static extern Int32 ReleaseDC(IntPtr hwnd, IntPtr hdc);

[DllImport("gdi32.dll")]
      static extern uint GetPixel(IntPtr hdc, int nXPos, int nYPos);
   
      static public System.Drawing.Color GetPixelColor(int x, int y)
      {
           IntPtr hdc = GetDC(IntPtr.Zero);
           uint pixel = GetPixel(hdc, x, y);
           ReleaseDC(IntPtr.Zero, hdc);
           Color color = Color.FromArgb((int)(pixel & 0x000000FF),
                                        (int)(pixel & 0x0000FF00) >> 8,
                                        (int)(pixel & 0x00FF0000) >> 16);
           return color;
      }
   }

!!!!Alternative Managed API:
Do you know one?  Please contribute it!

Documentation: GetPixel@msdn on MSDN, Color@msdn on MSDN