HWND TO BMP FILE (WIN32)

int __stdcall HwndToBmpFile(HWND hwnd, char *pszflname)
{
  HDC memdc, hdc;
  HANDLE hfl;
  DWORD dwBytes, dwNumColors;
  void *pBits;
  HBITMAP hbmp;
  BITMAPFILEHEADER fileheader;
  BITMAPINFOHEADER infoheader;
  RGBQUAD colors[256];
  BITMAPINFO bmpinfo;
  HGDIOBJ hret;
  RECT rct;
  hdc = GetWindowDC(hwnd);
  if(!hdc) return 0;
  GetWindowRect(hwnd, &rct);
  rct.bottom -= rct.top;
  rct.right -= rct.left;
  rct.top = GetDeviceCaps(hdc, BITSPIXEL);
  if(rct.top <= 8) dwNumColors = 256;
  else dwNumColors = 0;
  if(!(memdc = CreateCompatibleDC(hdc))) goto relHwndDc;
  bmpinfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
  bmpinfo.bmiHeader.biWidth = rct.right;
  bmpinfo.bmiHeader.biHeight = rct.bottom;
  bmpinfo.bmiHeader.biPlanes = 1;
  bmpinfo.bmiHeader.biBitCount = (WORD) rct.top;
  bmpinfo.bmiHeader.biCompression = BI_RGB;
  bmpinfo.bmiHeader.biSizeImage = 0;
  bmpinfo.bmiHeader.biXPelsPerMeter = 0;
  bmpinfo.bmiHeader.biYPelsPerMeter = 0;
  bmpinfo.bmiHeader.biClrUsed = dwNumColors;
  bmpinfo.bmiHeader.biClrImportant = dwNumColors;
  hbmp = CreateDIBSection(hdc, &bmpinfo, DIB_PAL_COLORS, &pBits, NULL, 0);
  if(!hbmp) goto errato;
  hret = SelectObject(memdc, hbmp);
  if(!hret || (hret == HGDI_ERROR)) goto errato;
  if(!BitBlt(memdc, 0, 0, rct.right, rct.bottom, hdc, 0, 0, SRCCOPY)) goto errato;
  if(dwNumColors) dwNumColors = GetDIBColorTable(memdc, 0, dwNumColors, colors);
  fileheader.bfType = 0x4D42;
  rct.left = dwNumColors * sizeof(RGBQUAD);
  fileheader.bfSize = ((rct.right * rct.bottom * rct.top) >> 3) + rct.left + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
  fileheader.bfReserved1 = fileheader.bfReserved2 = 0;
  fileheader.bfOffBits = rct.left + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
  infoheader.biSize = sizeof(BITMAPINFOHEADER);
  infoheader.biWidth = rct.right;
  infoheader.biHeight = rct.bottom;
  infoheader.biPlanes = 1;
  infoheader.biBitCount = (WORD) rct.top;
  infoheader.biCompression = BI_RGB;
  infoheader.biSizeImage = infoheader.biClrImportant = 0;
  infoheader.biXPelsPerMeter = infoheader.biYPelsPerMeter = 0;
  infoheader.biClrUsed = dwNumColors;
  hfl = CreateFile(pszflname,GENERIC_WRITE,0,0,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,0);
  if(hfl == INVALID_HANDLE_VALUE) {DeleteObject(hbmp); goto errato;}
  WriteFile(hfl, &fileheader, sizeof(BITMAPFILEHEADER), &dwBytes, 0);
  WriteFile(hfl, &infoheader, sizeof(BITMAPINFOHEADER), &dwBytes, 0);
  if(!dwNumColors) WriteFile(hfl, colors, rct.left, &dwBytes, 0);
  WriteFile(hfl, pBits, (rct.right * rct.bottom * rct.top) >> 3, &dwBytes, 0);
  CloseHandle(hfl);
  DeleteObject(hbmp);
  DeleteDC(memdc);
  return 1;
errato:
  DeleteDC(memdc);
relHwndDc:
  ReleaseDC(hwnd, hdc); return 0;
}