Конвертировать Windows BITMAP в PIX (беззнаковый буфер символов)

Я делаю скриншот окна, чтобы обработать его Leptonica а позже сделайте некоторое OCR с Tesseract

Проблема в том, что в плане производительности я бы хотел избежать записи и чтения BMP на диск и просто работать в памяти. Вот как я делаю скриншот:

int width, height = 0;

HDC hdcWindow;
HDC hdcMemDC = NULL;
HBITMAP hbmScreen = NULL;
BITMAP bmpScreen;

// Retrieve the handle to a display device context for the client
// area of the window.
//hdcScreen = GetDC(NULL);
//hdcWindow = GetDC(hWnd);

hdcWindow = GetDC(hWnd);

// Create a compatible DC which is used in a BitBlt from the window DC
hdcMemDC = CreateCompatibleDC(hdcWindow);

if (!hdcMemDC)
{
MessageBox(hWnd, L"CreateCompatibleDC has failed", L"Failed", MB_OK);
goto done;
}

// Get the client area for size calculation
RECT rcClient;
GetClientRect(hWnd, &rcClient);// Create a compatible bitmap from the Window DC
hbmScreen = CreateCompatibleBitmap(hdcWindow, rcClient.right - rcClient.left, rcClient.bottom - rcClient.top);

if (!hbmScreen)
{
MessageBox(hWnd, L"CreateCompatibleBitmap Failed", L"Failed", MB_OK);
goto done;
}

// Select the compatible bitmap into the compatible memory DC.
SelectObject(hdcMemDC, hbmScreen);

// Bit block transfer into our compatible memory DC.
if (!BitBlt(hdcMemDC,
0, 0,
rcClient.right - rcClient.left, rcClient.bottom - rcClient.top,
hdcWindow,
0, 0,
SRCCOPY))
{
MessageBox(hWnd, L"BitBlt has failed", L"Failed", MB_OK);
goto done;
}

// Get the BITMAP from the HBITMAP
GetObject(hbmScreen, sizeof(BITMAP), &bmpScreen);

BITMAPFILEHEADER   bmfHeader;
BITMAPINFOHEADER   bi;

bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bmpScreen.bmWidth;
bi.biHeight = bmpScreen.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = 32;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

DWORD dwBmpSize = ((bmpScreen.bmWidth * bi.biBitCount + 31) / 32) * 4 * bmpScreen.bmHeight;

// Starting with 32-bit Windows, GlobalAlloc and LocalAlloc are implemented as wrapper functions that
// call HeapAlloc using a handle to the process's default heap. Therefore, GlobalAlloc and LocalAlloc
// have greater overhead than HeapAlloc.
HANDLE hDIB = GlobalAlloc(GHND, dwBmpSize);
char *lpbitmap = (char *)GlobalLock(hDIB);

// Gets the "bits" from the bitmap and copies them into a buffer
// which is pointed to by lpbitmap.
GetDIBits(hdcWindow, hbmScreen, 0,
(UINT)bmpScreen.bmHeight,
lpbitmap,
(BITMAPINFO *)&bi, DIB_RGB_COLORS);

// A file is created, this is where we will save the screen capture.
HANDLE hFile = CreateFile(L"pics/UI.bmp",
GENERIC_WRITE,
0,
NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL, NULL);

// Add the size of the headers to the size of the bitmap to get the total file size
DWORD dwSizeofDIB = dwBmpSize + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);

//Offset to where the actual bitmap bits start.
bmfHeader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER);

//Size of the file
bmfHeader.bfSize = dwSizeofDIB;

//bfType must always be BM for Bitmaps
bmfHeader.bfType = 0x4D42; //BM

DWORD dwBytesWritten = 0;
WriteFile(hFile, (LPSTR)&bmfHeader, sizeof(BITMAPFILEHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)&bi, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
WriteFile(hFile, (LPSTR)lpbitmap, dwBmpSize, &dwBytesWritten, NULL);

//Unlock and Free the DIB from the heap
GlobalUnlock(hDIB);
GlobalFree(hDIB);

//Close the handle for the file that was created
CloseHandle(hFile);

width = rcClient.right - rcClient.left;
height = rcClient.bottom - rcClient.top;

//Clean up
done:
DeleteObject(hbmScreen);
DeleteObject(hdcMemDC);
ReleaseDC(hWnd, hdcWindow);

И вот как я это прочитал:

PIX* pixUI = pixRead("pics/UI.bmp");

Итак, я видел, что библиотека имеет PIX * pixReadMemBmp ( const l_uint8 *cdata, size_t size ) метод который занимает l_uint8 который является unsigned char буфер

Проблема в том, что я не понимаю, как я могу получить такой буфер от моего HBITMAP или же BITMAP объект.