使用.NET与GDI+实现不规则图形裁剪

转自：http://www.cnblogs.com/ruimingde/archive/2012/01/12/2321005.html


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

using System.Runtime.InteropServices;
using System.Drawing.Drawing2D;


namespace Ly.ImageLibrary
{
   public  class PngImage
    {
        [DllImport("gdi32.dll")]
        public static extern IntPtr ExtCreateRegion(IntPtr lpXform, uint nCount,
            ref byte lpRgnData);

        public static int RGN_AND = 1;
        public static int RGN_OR = 2;
        public static int RGN_XOR = 3;
        public static int RGN_DIFF = 4;
        public static int RGN_COPY = 5;
        public static int RGN_MIN = RGN_AND;
        public static int RGN_MAX = RGN_COPY;

        [DllImport("gdi32.dll")]
        public static extern int CombineRgn(IntPtr hrgnDest, IntPtr hrgnSrc1, IntPtr hrgnSrc2,
            int fnCombineMode);

        [DllImport("gdi32.dll")]
        public static extern bool DeleteObject(IntPtr hObject);

        public static Region ImageToRegion(Image AImage, Color ATransparent)
        {
            //转贴请注明出处ZswangY37(wjhu111#21cn.com) 时间2007-05-25
            if (AImage == null) return null;
            Bitmap vBitmap = new Bitmap(AImage);
            BitmapData vBitmapData = vBitmap.LockBits(new Rectangle(0, 0, vBitmap.Width, vBitmap.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppRgb);
            int vAddress = (int)vBitmapData.Scan0;
            int vOffset = vBitmapData.Stride - vBitmap.Width * 4; // 每行多出的字节数
            int h = vBitmap.Height, w = vBitmap.Width;
            int vTransparent = ColorTranslator.ToWin32(ATransparent); // 透明色
            int vAllocRect = (0x1000 - sizeof(uint) * 8) / sizeof(int); // 预分配的矩形数
            if (h * w < vAllocRect) vAllocRect = h * w;

            Byte[] vBuffer = new byte[sizeof(uint) * 8 + sizeof(int) * 4 * vAllocRect];
            //头信息dwSize\iType\nCount\nRegSize
            uint vCount = 0;
            vBuffer[0] = sizeof(uint) * 8; //dwSize//头信息大小
            vBuffer[4] = 1; //iType//int RDH_RECTANGLES = 1;//数据类型
            IntPtr vResult = IntPtr.Zero;

            uint vPointer = sizeof(uint) * 8;
            bool vWriteRect = false;