截透明

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Drawing;

namespace CSharpWin
{
    /* 作者：Starts_2000
     * 日期：2009-09-08
     * 网站：http://www.csharpwin.com/ CS 程序员之窗。
     * 你可以免费使用或修改以下代码，但请保留版权信息。
     * 具体请查看 CS程序员之窗开源协议（http://www.csharpwin.com/csol.html）。
     */

    internal class NativeMethods
    {
        public const int WS_EX_TRANSPARENT = 0x00000020;

[DllImport("user32.dll")]
public static extern bool ClipCursor(ref RECT lpRect);

[DllImport("user32.dll")]
public static extern IntPtr GetDesktopWindow();

[DllImport("user32.dll")]
public static extern IntPtr GetDC(IntPtr ptr);

[DllImport("user32.dll")]
public static extern int ReleaseDC(IntPtr hwnd, IntPtr hDC);

        [DllImport("gdi32.dll")]
        public static extern bool BitBlt(
            IntPtr hObject, int nXDest, int nYDest, int nWidth,
           int nHeight, IntPtr hObjSource, int nXSrc, int nYSrc,
            TernaryRasterOperations dwRop);

[DllImport("kernel32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr LoadLibrary(string lpFileName);

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;

            public RECT(int left, int top, int right, int bottom)
            {
                Left = left;
                Top = top;
                Right = right;
                Bottom = bottom;
            }

            public RECT(Rectangle rect)
            {
                Left = rect.Left;
                Top = rect.Top;
                Right = rect.Right;
                Bottom = rect.Bottom;
            }

            public Rectangle Rect
            {
                get
                {
                    return new Rectangle(
                        Left,
                        Top,
                        Right - Left,
                        Bottom - Top);
                }
            }

            public Size Size
            {
                get
                {
                    return new Size(Right - Left, Bottom - Top);
                }
            }

            public static RECT FromXYWH(int x, int y, int width, int height)
            {
                return new RECT(x,
                                y,
                                x + width,
                                y + height);
            }

            public static RECT FromRectangle(Rectangle rect)
            {
                return new RECT(rect.Left,
                                 rect.Top,
                                 rect.Right,
                                 rect.Bottom);
            }
        }

        public enum TernaryRasterOperations
        {
            SRCCOPY = 0x00CC0020, /* dest = source*/
            SRCPAINT = 0x00EE0086, /* dest = source OR dest*/
            SRCAND = 0x008800C6, /* dest = source AND dest*/
            SRCINVERT = 0x00660046, /* dest = source XOR dest*/
            SRCERASE = 0x00440328, /* dest = source AND (NOT dest )*/
            NOTSRCCOPY = 0x00330008, /* dest = (NOT source)*/
            NOTSRCERASE = 0x001100A6, /* dest = (NOT src) AND (NOT dest) */
            MERGECOPY = 0x00C000CA, /* dest = (source AND pattern)*/
            MERGEPAINT = 0x00BB0226, /* dest = (NOT source) OR dest*/
            PATCOPY = 0x00F00021, /* dest = pattern*/
            PATPAINT = 0x00FB0A09, /* dest = DPSnoo*/
            PATINVERT = 0x005A0049, /* dest = pattern XOR dest*/
            DSTINVERT = 0x00550009, /* dest = (NOT dest)*/
            BLACKNESS = 0x00000042, /* dest = BLACK*/
            WHITENESS = 0x00FF0062, /* dest = WHITE*/
            CAPTUREBLT = 0x40000000,//截透明图
        }
    }
}