BitBlt转换为字节数组并从c ++解析为c#

我正在尝试在C++中创建一个屏幕捕获DLL，并将生成的字节数组发送到C#。

我能够将大小返回到 C#，但字节数组始终为空。

这是C++代码(由我在互联网上找到的位组成(

__declspec(dllexport) int ScreenCap(BYTE* *data, DWORD *size)
{
try
{
//BITMAP bmpScreen;
HWND DesktopHwnd = GetDesktopWindow();
RECT DesktopParams;
HDC DevC = GetDC(DesktopHwnd);
GetWindowRect(DesktopHwnd,&DesktopParams);
DWORD Width = DesktopParams.right - DesktopParams.left;
DWORD Height = DesktopParams.bottom - DesktopParams.top;
DWORD FileSize = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)+(sizeof(RGBTRIPLE)+1*(Width*Height*4));
*size = FileSize;
char *BmpFileData = (char*)GlobalAlloc(0x0040,FileSize);
PBITMAPFILEHEADER BFileHeader = (PBITMAPFILEHEADER)BmpFileData;
PBITMAPINFOHEADER  BInfoHeader = (PBITMAPINFOHEADER)&BmpFileData[sizeof(BITMAPFILEHEADER)];
BFileHeader->bfType = 0x4D42; // BM
BFileHeader->bfSize = sizeof(BITMAPFILEHEADER);
BFileHeader->bfOffBits = sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER);
BInfoHeader->biSize = sizeof(BITMAPINFOHEADER);
BInfoHeader->biPlanes = 1;
BInfoHeader->biBitCount = 24;
BInfoHeader->biCompression = BI_RGB;
BInfoHeader->biHeight = Height;
BInfoHeader->biWidth = Width;
RGBTRIPLE *Image = (RGBTRIPLE*)&BmpFileData[sizeof(BITMAPFILEHEADER)+sizeof(BITMAPINFOHEADER)];
RGBTRIPLE color;
HDC CaptureDC = CreateCompatibleDC(DevC);
HBITMAP CaptureBitmap = CreateCompatibleBitmap(DevC,Width,Height);
SelectObject(CaptureDC,CaptureBitmap);
BOOL bRet = BitBlt(CaptureDC,0,0,Width,Height,DevC,0,0,SRCCOPY|CAPTUREBLT);
//GetDIBits(CaptureDC,CaptureBitmap,0,Height,Image,(LPBITMAPINFO)BInfoHeader, DIB_RGB_COLORS);
//GetObject(CaptureBitmap,sizeof(BITMAPFILEHEADER),&bmpScreen);
//BYTE* lpPixels = new BYTE[sizeof((LPBITMAPINFO)BInfoHeader)];
GetDIBits(CaptureDC, CaptureBitmap, 0, Height, *data, (LPBITMAPINFO)BInfoHeader, DIB_RGB_COLORS);
//DWORD Junk;
//DIBSECTION dib;
//GetObject(CaptureBitmap, sizeof(dib), (LPVOID)&dib);
//HANDLE FH = CreateFileA(BmpName,GENERIC_WRITE,FILE_SHARE_WRITE,0,CREATE_ALWAYS,0,0);
//WriteFile(FH,BmpFileData,FileSize,&Junk,0);
//CloseHandle(FH);
GlobalFree(BmpFileData); 

return 1;
}
catch(char *p)
{
return 0;
}
}

这是我与"ref"关键字一起使用的 C# 代码。

[DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
static extern int ScreenCap(ref byte[] data, ref int size);
public static void CapScreen()
{
try
{
int hr = 0;
byte[] gData = null;
int gSize = 0;
hr = ScreenCap(ref gData, ref gSize);
int a = 1;
}
catch(Exception ex)
{
int a = 1;
}

我认为我的 GetDIBits 可能有问题，但我不确定。我希望你们中的一些上师能让我走上正确的道路。谢谢。

*编辑*

好的 非常感谢jdweng和filip为我指出正确的方向。 我现在将屏幕作为 IntPtr 接收，并能够将其呈现到我的 C# 应用程序。 这是现在可以工作的代码(我将在底部解释(

__declspec(dllexport) char* ScreenCap(DWORD * size)

{ 尝试 { 获取屏幕尺寸 int nScreenWidth = GetSystemMetrics(SM_CXSCREEN(; int nScreenHeight = GetSystemMetrics(SM_CYSCREEN(;

*size = ((((24 * nScreenWidth + 31)&(~31)) / 8)*nScreenHeight);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader); 
// Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
HDC hdcScreen = GetDC(GetDesktopWindow());
HDC hdcCompatible  = CreateCompatibleDC(hdcScreen);
HBITMAP hBmp = CreateCompatibleBitmap(hdcScreen, nScreenWidth, nScreenHeight);
//HGDIOBJ hOldBmp = SelectObject(hdcCompatible, hBmp); 
HGDIOBJ hOldBmp = (HGDIOBJ) SelectObject(hdcCompatible, hBmp);
BOOL bOK = BitBlt(hdcCompatible,0,0,nScreenWidth, nScreenHeight, hdcScreen,0,0,SRCCOPY|CAPTUREBLT); 
SelectObject(hdcCompatible, hOldBmp); // always select the previously selected object once done
// Get the BITMAPINFO structure from the bitmap
GetDIBits(hdcScreen, hBmp, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS);
// create the bitmap buffer
char* lpPixels = new char[MyBMInfo.bmiHeader.biSizeImage];
MyBMInfo.bmiHeader.biCompression = BI_RGB; 
MyBMInfo.bmiHeader.biBitCount = 24;  
// get the actual bitmap buffer
GetDIBits(hdcScreen, hBmp, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS);
//Clean Up
DeleteDC(hdcCompatible);
ReleaseDC(GetDesktopWindow(), hdcScreen);
DeleteDC(hdcScreen);
DeleteObject(hBmp);
//DeleteObject(hOldBmp);
return lpPixels;
}
catch(char *p)
{
return 0;
}

}

和 C#

[DllImport("consoleapplication1.dll", CallingConvention = CallingConvention.Cdecl)]
static extern IntPtr ScreenCap(ref int size);
while(true)
{
int size = 0;
IntPtr ptr = ScreenCap(ref size);
byte[] result = new byte[size];
Marshal.Copy(ptr, result, 0, size);
Marshal.Release(ptr);
ptr = IntPtr.Zero;
MainWindow.Dispatcher.Invoke(new Action(
() =>
{
System.Windows.Media.ImageSource ThumbnailImage = System.Windows.Media.Imaging.BitmapSource.Create(1920, 1080, 96, 96, System.Windows.Media.PixelFormats.Bgr24, null, result, 1920 * 3);
MainWindow.canvasMain.Background = new System.Windows.Media.ImageBrush(ThumbnailImage);
result = null;
GC.Collect();
GC.WaitForPendingFinalizers();
}
), null);
}

不确定我现在面临的问题是否是由于这样做造成的，但我现在从 C++ dll 中获得了重大内存泄漏。如果这是另一个问题，我是否需要创建新线程？

**编辑**

通过在 C++ dll 中创建一个新函数来删除返回的 char 数组解决了问题。 可能不优雅，但它有效。

我要非常感谢菲利普，他的评论帮助我看了各种地方，看到了其他东西。Jdweng，你的IntPtr是天赐之物。不知道我是如何设置这个的，由Jdweng回答。很想奖励你们俩。