VC++编程：调整位图尺寸技术实现

LPBYTE FindDIBBits(LPBYTE lpDIB) 
{ 
   return (lpDIB + *(LPDWORD)lpDIB + 0); 
} 
DWORD BytesPerLine(LPBYTE lpDIB) 
{ 
    return WIDTHBYTES(((LPBITMAPINFOHEADER)lpDIB)->biWidth * ((LPBITMAPINFOHEADER)lpDIB)->biPlanes * ((LPBITMAPINFOHEADER)lpDIB)->biBitCount); 
} 
HDIB CChangeSizeDlg::ChangeDIBSize(HDIB hDIB, int nWidth, int nHeight)
{
    LPBITMAPINFO lpbmi = NULL; 
    LPBYTE       lpSourceBits, lpTargetBits, lpResult; 
    HDC  hDC = NULL, hSourceDC, hTargetDC; 
    HBITMAP      hSourceBitmap, hTargetBitmap, hOldTargetBitmap, hOldSourceBitmap; 
    DWORD        dwSourceBitsSize, dwTargetBitsSize, dwTargetHeaderSize; 
HDIB  hNewDIB;
DWORD  dwSize;

WaitCursorBegin();

// Get DIB pointer
if (! hDIB)
{
WaitCursorEnd();
return NULL;
}
LPBITMAPINFO lpSrcDIB = (LPBITMAPINFO)GlobalLock(hDIB);
if (! lpSrcDIB)
{
WaitCursorEnd();

return NULL;
}

    // Allocate and fill out a BITMAPINFO struct for the new DIB 
    dwTargetHeaderSize = sizeof( BITMAPINFOHEADER ) + 0; 
    lpbmi = (LPBITMAPINFO)malloc( dwTargetHeaderSize ); 
memcpy(lpbmi, lpSrcDIB, dwTargetHeaderSize);
    lpbmi->bmiHeader.biWidth = nWidth; 
    lpbmi->bmiHeader.biHeight = nHeight; 
 
    // Gonna use DIBSections and BitBlt() to do the conversion, so make 'em 
hDC = ::GetDC( NULL ); 
    hTargetBitmap = CreateDIBSection( hDC, lpbmi, DIB_RGB_COLORS, (VOID **)&lpTargetBits, NULL, 0 ); 
    hSourceBitmap = CreateDIBSection( hDC, lpSrcDIB, DIB_RGB_COLORS, (VOID **)&lpSourceBits, NULL, 0 ); 
    hSourceDC = CreateCompatibleDC( hDC ); 
    hTargetDC = CreateCompatibleDC( hDC ); 
  
    // Flip the bits on the source DIBSection to match the source DIB 
    dwSourceBitsSize = lpSrcDIB->bmiHeader.biHeight * BytesPerLine((LPBYTE)&(lpSrcDIB->bmiHeader)); 
    dwTargetBitsSize = lpbmi->bmiHeader.biHeight * BytesPerLine((LPBYTE)&(lpbmi->bmiHeader)); 
    memcpy( lpSourceBits, FindDIBBits((LPBYTE)lpSrcDIB), dwSourceBitsSize ); 
    lpbmi->bmiHeader.biSizeImage = dwTargetBitsSize; 
 
    // Select DIBSections into DCs 
    hOldSourceBitmap = (HBITMAP)SelectObject( hSourceDC, hSourceBitmap ); 
    hOldTargetBitmap = (HBITMAP)SelectObject( hTargetDC, hTargetBitmap ); 
 
// put old bitmap in new bitmap 
    SetStretchBltMode( hTargetDC, COLORONCOLOR ); 
    StretchBlt( hTargetDC, 0, 0, lpbmi->bmiHeader.biWidth, lpbmi->bmiHeader.biHeight, hSourceDC, 0, 0, lpSrcDIB->bmiHeader.biWidth, lpSrcDIB->bmiHeader.biHeight, SRCCOPY );