C / C++ / MFC

void CDemoDialog::OnPaint()
{
   CPaintDC dc(this); // device context for painting
 
   // transfer the bitmap into paint DC using a transparent color  
   dc.TransparentBlt(
      10, 10, bmp.bmWidth, bmp.bmHeight, // destination coordinates and sizes
      &pDCTmp,                           // source DC .. your DC with bitmap
      0, 0, bmp.bmWidth, bmp.bmHeight,   // source coordinates and sizes
      RGB(255, 0, 0));                   // transparent color

}

int DialogFromTemplate (HWND parent, int DialogWth, int DialogHt, char* DlgTitle, DLGPROC handler)
{
   int nchar, ret;
   int x, y;
   RECT r;
   HGLOBAL hgbl;
   LPDLGTEMPLATE lpdt;
   LPWORD lpw;
   LPWSTR lpwsz;

   GetClientRect(parent, &r);	 	                                      // Get parent client area
   x =  ((r.right+r.left)/2);		                                     // Calc x client centre position
   y = ((r.bottom+r.top)/2);		                                     // Calc y client centre position

    /* from the client centre the dialog left is half width and top half height less */
    x -= DialogWth/2;
    y -= DialogHt/2;

   /* template size and position are in multiples of 2 .. yeah its weird */
    x /= 2;				                                       // X client left position in template units
    y /= 2;				                                       // Y client top position in template units
	
   hgbl = GlobalAlloc(GMEM_ZEROINIT, 1024);                               // Allocate memory
   if (!hgbl) return -1;		 	                                      // If allocate fail exit
   lpdt = (LPDLGTEMPLATE)GlobalLock(hgbl);                              // Lock the allocated memory
   lpdt->style = WS_POPUP | WS_CAPTION | WS_SYSMENU;  // Window style
   lpdt->cdit = 0;					  // Number of controls
   lpdt->x  = x;					  // X position
   lpdt->y  = y;					  // Y psoition
   lpdt->cx = DialogWth/2;				  // Window width (template units)
   lpdt->cy = DialogHt/2;				  // Window height (template units)
   lpw = (LPWORD)(lpdt + 1);				  // Set pointer address
   *lpw++ = 0;					  // No menu
   *lpw++ = 0;					  // Predefined dialog box class (by default)
   lpwsz = (LPWSTR)lpw;				  // Typecast pointer
   nchar = 1 + MultiByteToWideChar(CP_ACP, 0, DlgTitle, 
	  -1, lpwsz, 50);				  // Title of dialog
   lpw += nchar;					  // Increment by size of name
   *lpw++ = 0;					  // No creation data
   GlobalUnlock(hgbl);				  // Release lock on the memory block 
   ret = (int)DialogBoxIndirectParam(GetModuleHandle(0), 
     (LPDLGTEMPLATE)hgbl, parent, Handler,  0);		  // Create the dialog from template
   GlobalFree(hgbl);					  // Free the allocated memory
    return ret;				 	  // Return result
}

RECT R1, R2;
GetClientRect(GetParent(Wnd), &R1);      // Parent client area
GetWindowRect(Wnd, &R2);                 // Dialog area
SetWindowPos(Wnd, 0, 
             (R1.right+R1.left)/2 - (R2.right-R2.left)/2 ,  // Parent x centre - half dialog width
             (R1.top+R1.Bottom)/2 - (R2.bottom-R2.top)/2,   // Parent y centre - half  dialog height
              0, 0,                                         // No size data
              SWP_NOSIZE | SWP_NOACTIVATE | SWP_NOZORDER);

int Wth, Ht;
RECT R1, R2;
GetClientRect(GetParent(Wnd), &R1);          // Parent client area
GetWindowRect(Wnd, &R2);                     // Dialog area
Wth = (R2.right-R2.left) * numerator;        // Multiply dialog width by numerator
Wth /= denominator;                          // Divide dialog width by denominator
Ht = (R2.bottom-R2.top) * numerator;         // Multiply dialog height by numerator
Ht /= denominator;                           // Divide dialog height by denominator
SetWindowPos(Wnd, 0, 
             (R1.right+R1.left)/2 - Wth/2 ,  // Parent x centre - half scaled dialog width
             (R1.top+R1.Bottom)/2 - Ht/2,    // Parent y centre - half  dialog height
              Wth, Ht,                       // New sizes
              SWP_NOACTIVATE | SWP_NOZORDER);// Do not change order or activate

/* so if you want to scale the children windows you need to scale and move them */
/* now go thru each child by id (shown as xxx) and scale and move them with this */
RECT R3;
HWND cWnd = GetDlgItem(Wnd, xxxx);           // Fetch and hold child handle from xxxx id
GetWindowRect(cWnd, &R3);                    // Fetch the child area
R3.left *= numerator;                        // Multiply child window left by numerator
R3.left /= denominator;                      // Divide child window left by denominator
R3.right *= numerator;                       // Multiply child window right by numerator
R3.right /= denominator;                     // Divide child window right by denominator
R3.top *= numerator;                         // Multiply child window top by numerator
R3.top /= denominator;                       // Divide child window top by denominator
R3.bottom *= numerator;                      // Multiply child window bottom by numerator
R3.bottom /= denominator;                    // Divide child window bottom by denominator
SetWindowPos(cWnd, 0, 
             R3.left,                        // New child left
             R3.top,                         // New child top
             R3.right - R3.left,             // New child width
             R3.bottom - R3.top,             // New child height
             SWP_NOACTIVATE | SWP_NOZORDER); // Do not change order or activate

Alexander Kindel wrote:

...size the dialog box such that the distance between the left edge of the client region and the left edge of the leftmost control is the same as that between the right edge of the rightmost control and the right edge of the client region.

CreateObj(data)
Do work;;;
FreeObj(data)