Writing a window image to a BMP file

Same as Bmp2Bmp24(), but the input is not BMPPIXEL format but DC.
Usage: CWnd *DispWnd;
DispWnd=(CWnd *)GetDlgItem(IDC_IMAGE);
WriteWindowToDIB("AAB.BMP", DispWnd );

HANDLE DDBToDIB( CBitmap& bitmap, DWORD dwCompression, CPalette* pPal )
{
BITMAP bm;
BITMAPINFOHEADER bi;
LPBITMAPINFOHEADER lpbi;
DWORD dwLen;
HANDLE hDIB;
HANDLE handle;
HDC hDC;
HPALETTE hPal;


ASSERT( bitmap.GetSafeHandle() );

// The function has no arg for bitfields
if( dwCompression == BI_BITFIELDS )
return NULL;

// If a palette has not been supplied use defaul palette
hPal = (HPALETTE) pPal->GetSafeHandle();
if (hPal==NULL)
hPal = (HPALETTE) GetStockObject(DEFAULT_PALETTE);

// Get bitmap information
bitmap.GetObject(sizeof(bm),(LPSTR)&bm);

// Initialize the bitmapinfoheader
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = bm.bmWidth;
bi.biHeight = bm.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = bm.bmPlanes * bm.bmBitsPixel;
bi.biCompression = dwCompression;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = 0;
bi.biClrImportant = 0;

// Compute the size of the infoheader and the color table
int nColors = (1 << bi.biBitCount);
if( nColors > 256 )
nColors = 0;
dwLen = bi.biSize + nColors * sizeof(RGBQUAD);

// We need a device context to get the DIB from
hDC = GetDC(NULL);
hPal = SelectPalette(hDC,hPal,FALSE);
RealizePalette(hDC);

// Allocate enough memory to hold bitmapinfoheader and color table
hDIB = GlobalAlloc(GMEM_FIXED,dwLen);

if (!hDIB){
SelectPalette(hDC,hPal,FALSE);
ReleaseDC(NULL,hDC);
return NULL;
}

lpbi = (LPBITMAPINFOHEADER)hDIB;

*lpbi = bi;

// Call GetDIBits with a NULL lpBits param, so the device driver
// will calculate the biSizeImage field
GetDIBits(hDC, (HBITMAP)bitmap.GetSafeHandle(), 0L, (DWORD)bi.biHeight,
(LPBYTE)NULL, (LPBITMAPINFO)lpbi, (DWORD)DIB_RGB_COLORS);

bi = *lpbi;

// If the driver did not fill in the biSizeImage field, then compute it
// Each scan line of the image is aligned on a DWORD (32bit) boundary
if (bi.biSizeImage == 0){
bi.biSizeImage = ((((bi.biWidth * bi.biBitCount) + 31) & ~31) / 8)
* bi.biHeight;

// If a compression scheme is used the result may infact be larger
// Increase the size to account for this.
if (dwCompression != BI_RGB)
bi.biSizeImage = (bi.biSizeImage * 3) / 2;
}

// Realloc the buffer so that it can hold all the bits
dwLen += bi.biSizeImage;
if (handle = GlobalReAlloc(hDIB, dwLen, GMEM_MOVEABLE))
hDIB = handle;
else{
GlobalFree(hDIB);

// Reselect the original palette
SelectPalette(hDC,hPal,FALSE);
ReleaseDC(NULL,hDC);
return NULL;
}

// Get the bitmap bits
lpbi = (LPBITMAPINFOHEADER)hDIB;

// FINALLY get the DIB
BOOL bGotBits = GetDIBits( hDC, (HBITMAP)bitmap.GetSafeHandle(),
0L, // Start scan line
(DWORD)bi.biHeight, // # of scan lines
(LPBYTE)lpbi // address for bitmap bits
+ (bi.biSize + nColors * sizeof(RGBQUAD)),
(LPBITMAPINFO)lpbi, // address of bitmapinfo
(DWORD)DIB_RGB_COLORS); // Use RGB for color table

if( !bGotBits )
{
GlobalFree(hDIB);

SelectPalette(hDC,hPal,FALSE);
ReleaseDC(NULL,hDC);
return NULL;
}

SelectPalette(hDC,hPal,FALSE);
ReleaseDC(NULL,hDC);
return hDIB;
}



BOOL WriteDIB( LPTSTR szFile, HANDLE hDIB)
{
BITMAPFILEHEADER hdr;
LPBITMAPINFOHEADER lpbi;

if (!hDIB)
return FALSE;

CFile file;
if( !file.Open( szFile, CFile::modeWrite|CFile::modeCreate) )
return FALSE;

lpbi = (LPBITMAPINFOHEADER)hDIB;

int nColors = 1 << lpbi->biBitCount;

// Fill in the fields of the file header
hdr.bfType = ((WORD) ('M' << 8) | 'B'); // is always "BM"
hdr.bfSize = GlobalSize (hDIB) + sizeof( hdr );
hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;
hdr.bfOffBits = (DWORD) (sizeof( hdr ) + lpbi->biSize +
nColors * sizeof(RGBQUAD));

// Write the file header
file.Write( &hdr, sizeof(hdr) );

// Write the DIB header and the bits
file.Write( lpbi, GlobalSize(hDIB) );

return TRUE;
}

BOOL CTestOFDlg::WriteWindowToDIB( LPTSTR szFile, CWnd *pWnd )
{
CBitmap bitmap;
CWindowDC dc(pWnd);
CDC memDC;
CRect rect;

memDC.CreateCompatibleDC(&dc);

pWnd->GetWindowRect(rect);

bitmap.CreateCompatibleBitmap(&dc, rect.Width(),rect.Height() );

CBitmap* pOldBitmap = memDC.SelectObject(&bitmap);
memDC.BitBlt(0, 0, rect.Width(),rect.Height(), &dc, 0, 0, SRCCOPY);

// Create logical palette if device support a palette
CPalette pal;
if( dc.GetDeviceCaps(RASTERCAPS) & RC_PALETTE )
{
UINT nSize = sizeof(LOGPALETTE) + (sizeof(PALETTEENTRY) * 256);
LOGPALETTE *pLP = (LOGPALETTE *) new BYTE[nSize];
pLP->palVersion = 0x300;

pLP->palNumEntries =
GetSystemPaletteEntries( dc, 0, 255, pLP->palPalEntry );

// Create the palette
pal.CreatePalette( pLP );

delete[] pLP;
}

memDC.SelectObject(pOldBitmap);

// Convert the bitmap to a DIB
HANDLE hDIB = DDBToDIB( bitmap, BI_RGB, &pal );

if( hDIB == NULL )
return FALSE;

// Write it to file
WriteDIB( szFile, hDIB );

// Free the memory allocated by DDBToDIB for the DIB
GlobalFree( hDIB );
return TRUE;
}