Fitting an Image to a Window

/* Global declarations */   
RECT rWndSize;   /* RECT for sizing the window. */   
RECT rClientSize;   /* RECT for the client area. */   
RECT rLeadDest;   /* RECT for the destination rectangle for painting. */        
RECT rLeadSource;   /* RECT for the source rectangle for painting. */     
HPALETTE hpalPaint;   /* Paint palette handle. */   
BITMAPHANDLE LeadBitmap;  /* Bitmap handle for the loaded image. */   
L_INT DisplayWidth, DisplayHeight;  /* Dimensions of the displayed image */   
/* Local declarations in the message-processing function */   
PAINTSTRUCT ps; /* Structure for processing the WM_PAINT message */   
HPALETTE hPalette = NULL; /* Temporary copy of the current system palette */   
HDC hdc; /* Device context used with the palette functions */   
int AdjustedWidth, AdjustedHeight; /* Adjusted dimensions of the window */ 

/* Get the current window size and client area */   
GetWindowRect(hWnd, &rWndSize);   
GetClientRect(hWnd,&rClientSize);   
/* Use this user-defined function to fit the displayed image in the client area. */   
CalcDisplay (  rClientSize.right,   /* Width allowed */   
               rClientSize.bottom,  /* Height allowed */   
               BITMAPWIDTH(&LeadBitmap),    /* Width factor, for aspect ratio */   
               BITMAPHEIGHT(&LeadBitmap),   /* Height factor, for aspect ratio */      
               NULL,                /* Resulting left value, not used */   
               NULL,                /* Resulting top value, not used */   
               &DisplayWidth,       /* Resulting width value */   
               &DisplayHeight);     /* Resulting height value */   
/* Adjust the window size to remove blank space at the right or bottom */   
AdjustedWidth = rWndSize.right - rWndSize.left + DisplayWidth - rClientSize.right;   
AdjustedHeight = rWndSize.bottom - rWndSize.top + DisplayHeight - rClientSize.bottom;   
MoveWindow(hWnd, rWndSize.left, rWndSize.top, AdjustedWidth, AdjustedHeight, FALSE);   
/* Get the client area of the adjusted window */   
GetClientRect(hWnd,&rClientSize);   
/* Make the destination rectangle for painting the same as the client area */   
rLeadDest = rClientSize;   
/* Set the source rectangle to use the whole bitmap */   
SetRect(&rLeadSource, 0, 0, LeadBitmap.Width, LeadBitmap.Height); 

case WM_PAINT: 
/* Get the handle to the device context */ 
hdc = BeginPaint (hWnd, &ps); 
if (LeadBitmap.Flags.Allocated)  /* Do we have an image? */ 
{ 
   if (hpalPaint) /* If we have a paint palette, select it */ 
   { 
      hPalette = SelectPalette (hdc, hpalPaint, FALSE); 
      /* Uncomment this if you do not process WM_QUERYNEWPALETTE */ 
      /* RealizePalette (hdc); */ 
   } 
   /* Paint the image */ 
   L_PaintDC (hdc, 
   &LeadBitmap, 
   &rLeadSource,   /* Source rectangle */ 
   NULL,           /* Default source clip area */ 
   &rLeadDest,     /* Destination rectangle */ 
   &ps.rcPaint,    /* Dest clip set by WM_PAINT */ 
   SRCCOPY);       /* Normal Paint */ 
   if (hpalPaint)         /* Return the old palette */ 
      SelectPalette (hdc, hPalette, FALSE); 
} 
EndPaint (hWnd, &ps);     /* Return the DC */ 
return (0); 

void CalcDisplay (L_INT WidthAllowed, L_INT HeightAllowed, 
L_INT WidthFactor, L_INT HeightFactor, 
L_INT *ResultLeft, L_INT *ResultTop, 
L_INT *ResultWidth, L_INT *ResultHeight) 
{ 
   /* Local variables for calculating results */ 
   L_INT Left, Top, Width, Height; 
   /* See if using the maximum width will make the image too tall */ 
   if(MulDiv(WidthAllowed, HeightFactor, WidthFactor) < HeightAllowed) 
   { /* Use the maximum width, and calculate the height and top values */ 
      Left = 0; 
      Width = WidthAllowed; 
      Height = MulDiv(Width, HeightFactor, WidthFactor); 
      Top = (HeightAllowed - Height) / 2; 
   } 
   else 
   { /* Use the maximum height, and calculate the width and left values */ 
      Top = 0; 
      Height = HeightAllowed; 
      Width = MulDiv(Height, WidthFactor, HeightFactor); 
      Left = (WidthAllowed - Width) / 2; 
   } 
   /* Update the top and left results, if the caller did not pass NULL */ 
   if (ResultTop != NULL) 
      *ResultTop = Top; 
   if (ResultLeft != NULL) 
      *ResultLeft = Left; 
   /* Update the width and height results */ 
   *ResultWidth = Width; 
   *ResultHeight = Height; 
   return; 
}