Fitting an Image to a Window

Show in webframe

If you are using the high-level LBitmapWindow (or derived) class, you can use the LBitmapWindow::SetZoomMode function to zoom an image in the following manners:

ZOOM_FIT	to fit the bitmap in the window while maintaining the aspect ratio.
ZOOM_STRETCH	to stretch the bitmap to the window.
ZOOM_NORMAL	to display the bitmap in its normal size.
ZOOM_FITWIDTH	to fit the bitmap to the width of the window.
ZOOM_FITHEIGHT	to fit the bitmap to the height of the window.

You can also use LBitmapWindow::FitToParent to fit the class object's window to it's parent.

If you are not using LBitmapWindow, to fit an image to a window, you only have to calculate a display rectangle that fits the window's client area, while preserving the image's aspect ratio. The following code snippets show how this can be done.

LBitmapBase LeadBitmap; //bitmap for the loading image

RECT rWndSize;
RECT rClientSize;
RECT rLeadDest;
L_INT WidthAllowed;
L_INT HeightAllowed;
L_INT WidthFactor;
L_INT HeightFactor;
L_INT Left, Top, Width, Height;
L_INT nRet;

/* Load the LEAD DLLs */
LBase LeadBase;
LeadBase.LoadLibraries(LT_ALL_LEADLIB);

/* Load an image */
nRet = LeadBitmap.Load(TEXT("v:\\images\\eagle.cmp"), 8);

/* Get the current window size and client area */
::GetWindowRect(this->m_hWnd, &rWndSize);
::GetClientRect(this->m_hWnd,&rClientSize);

/* Use this to fit the displayed image in the client area. */
WidthAllowed = rClientSize.right;
HeightAllowed = rClientSize.bottom;
WidthFactor = LeadBitmap.GetWidth();
HeightFactor = LeadBitmap.GetHeight();

/* 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 = 0;
}
else
{

   /* Use the maximum height, and calculate the width and left values */
   Top = 0;
   Height = HeightAllowed;
   Width = MulDiv(Height, WidthFactor, HeightFactor);
   Left = 0;
}

RECT rc;
/* Set the source rectangle to use the whole bitmap */
SetRect(&rc, 0, 0, LeadBitmap.GetWidth(), LeadBitmap.GetHeight());
LeadBitmap.SetSrcRect(&rc);
/* Set the source clipping rectangle to use the whole bitmap */
LeadBitmap.SetClipSrcRect(&rc);
/* Set the destination rectangles */
SetRect(&rLeadDest, Left, Top, Width, Height);
LeadBitmap.SetDstRect(&rLeadDest);
LeadBitmap.SetClipDstRect(&rLeadDest);

/* paint the image */
HDC hDC = ::GetDC(this->m_hWnd);
LeadBitmap.Paint()->SetDC(hDC);
LeadBitmap.Paint()->PaintDC();
::ReleaseDC(this->m_hWnd, hDC);