C#下调用GDI的遮罩功能得不到预期效果如何解决
引用API：[DllImport("gdi32.dll ")]
private static extern bool BitBlt(
IntPtr hdcDest, // handle to destination DC
int nXDest, // x-coord of destination upper-left corner
int nYDest, // y-coord of destination upper-left corner
int nWidth, // width of destination rectangle
int nHeight, // height of destination rectangle
IntPtr hdcSrc, // handle to source DC
int nXSrc, // x-coordinate of source upper-left corner
int nYSrc, // y-coordinate of source upper-left corner
uint dwRop // raster operation code
);
/* Ternary raster operations */
const uint SRCCOPY = 0x00CC0020; /* dest = source */
const uint SRCPAINT = 0x00EE0086; /* dest = source OR dest */
const uint SRCAND = 0x008800C6; /* dest = source AND dest */
const uint SRCINVERT = 0x00660046; /* dest = source XOR dest */
const uint SRCERASE = 0x00440328; /* dest = source AND (NOT dest ) */
const uint NOTSRCCOPY = 0x00330008; /* dest = (NOT source) */
const uint NOTSRCERASE = 0x001100A6; /* dest = (NOT src) AND (NOT dest) */
const uint MERGECOPY = 0x00C000CA; /* dest = (source AND pattern) */
const uint MERGEPAINT = 0x00BB0226; /* dest = (NOT source) OR dest */
const uint PATCOPY = 0x00F00021; /* dest = pattern */
const uint PATPAINT = 0x00FB0A09; /* dest = DPSnoo */
const uint PATINVERT = 0x005A0049; /* dest = pattern XOR dest */
const uint DSTINVERT = 0x00550009; /* dest = (NOT dest) */
const uint BLACKNESS = 0x00000042; /* dest = BLACK */
const uint WHITENESS = 0x00FF0062; /* dest = WHITE */
[DllImport("gdi32.dll")]
static public extern IntPtr CreateCompatibleDC(IntPtr hDC);
[DllImport("user32.dll", EntryPoint = "GetDC")]
public static extern IntPtr GetDC(IntPtr hWnd);
[DllImport("gdi32.dll")]
public static extern int SetROP2(int h, int op);
[DllImport("gdi32.dll")]
static public extern bool DeleteObject(IntPtr hObject);
[DllImport("gdi32.dll")]
static public extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);
[DllImport("gdi32.dll")]
static public extern IntPtr DeleteDC(IntPtr hDC);
功能实现：
Bitmap BmpB = new Bitmap("am.png");//am为遮罩图
Bitmap BmpA = new Bitmap("a.png");//a为要实现透明的图
Bitmap BmPBack = new Bitmap("b.png");//b是背景图，本帖附件给的是相关的图片
Graphics g = pictureBox1.CreateGraphics();
System.IntPtr hdc = g.GetHdc();
System.IntPtr BmPBackDC = CreateCompatibleDC(hdc);
System.IntPtr BmpADC = CreateCompatibleDC(hdc);
System.IntPtr BmpBDC = CreateCompatibleDC(hdc);
System.IntPtr Oldback = SelectObject(BmPBackDC, BmPBack.GetHbitmap());
System.IntPtr OldA = SelectObject(BmpADC, BmpA.GetHbitmap());
System.IntPtr OldB = SelectObject(BmpBDC, BmpB.GetHbitmap());
BitBlt(hdc, 0, 0, BmpA.Width, BmpA.Height, BmPBackDC, 0, 0, SRCCOPY);
BitBlt(hdc, 0, 0, BmpA.Width, BmpA.Height, BmpBDC, 0, 0, SRCAND);
BitBlt(hdc, 0, 0, BmpA.Width, BmpA.Height, BmpADC, 0, 0, SRCPAINT);
SelectObject(BmpBDC,OldB);
SelectObject(BmpADC,OldA);
SelectObject(BmPBackDC,Oldback);
g.ReleaseHdc();
DeleteDC(BmpADC);
DeleteDC(BmpBDC);
DeleteDC(BmPBackDC);
如题，个人写的这段代码不能实现利用遮罩的方式实现BMP图像透明效果，这段代码是仿照C++改的，C++代码如下：
void CDemoDlg::OnPaint()
{
CPaintDC dc(this);
CBitmap BmPBack,BmpA,BmpB,*pOldBack,*pOldA,*pOldB;
BmpBack.LoadBitmap(IDB_BACKGROUND); // 载入背景图
BmpA.LoadBitmap(IDB_BITMAPA); //载入图A
BmpB.LoadBitmap(IDB_BITMAPB); //载入图B
CDC dcBack,dcA,dcB; //声明三个内存DC用于画图
dcBack.CreateCompatibleDC(&dc);
dcA.CreateCompatibleDC(&dc);
dcB.CreateCompatibleDC(&dc); //把这三个内存DC创建成和PaintDC兼容的DC
pOldBack=dcBack.SelectObject(&BmpBack);
pOldA=dcA.SelectObject(&BmpA);
pOldB=dcB.SelectObject(&BmpB); //把三个位图选入相应的DC
dc.BitBlt(0,0,100,100,&dcBack,0,0,SRCCOPY); //画背景
dc.BitBlt(0,0,48,48,&dcB,0,0,SRCAND); //用与的方式画遮罩图B
dc.BitBlt(0,0,48,48,&dcA,0,0,SRCPAINT); //用或的方式画遮图A
个人还曾参考了这个地址上的文章，可是看了半天按照那个改还是不能实现预期功能：http://hi.baidu.com/char_string/blog/item/fa2a7b8b22cb047a9e2fb42b.html
求高手帮忙指正下问题所在 --------------------编程问答-------------------- 不要用那么复杂的 gdi+ 就可实现 不要总盯到一棵树 --------------------编程问答-------------------- 楼上，这个功能用GDI+是实现不了了，只有GDI能实现对位图的位操作。。。 --------------------编程问答-------------------- 用互操作，不如直接用C++ --------------------编程问答-------------------- 不知道楼主想要的透明效果是什么样子。
是不是跟你现在提供的图有关,尤其是背景图，
楼主可以对下面这三句进行调试，看看执行每一句是否是需要的效果（先注释掉第二、三句，然后恢复第二句，最后恢复第三句）。
--------------------编程问答-------------------- 帮顶 --------------------编程问答-------------------- up --------------------编程问答-------------------- 学习一下,等待高手的解决方案 --------------------编程问答-------------------- 这个是C++代码不是C#代码。。。。。。。 --------------------编程问答-------------------- 还是没人能帮忙解决么？
dc.BitBlt(0,0,100,100,&dcBack,0,0,SRCCOPY); //画背景
dc.BitBlt(0,0,48,48,&dcB,0,0,SRCAND); //用与的方式画遮罩图B
dc.BitBlt(0,0,48,48,&dcA,0,0,SRCPAINT); //用或的方式画遮图A
补充：.NET技术 , C#
