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Bitmap Topics: Displaying From a File
 

Introduction

It is usually easy to display a bitmap if you create it as a resource file. In some applications, you may want the user to select a picture from a medium and display it in a dialog box or another container. This involves a few steps but nothing particularly fancy.

Practical Learning Practical Learning: Displaying a Bitmap From a File

  1. Start Microsoft Visual C++ and create an MFC Application named FoodPreview1
  2. Create it as Dialog Based
  3. Delete the TODO static control and the OK button
  4. Add a Picture Control to the dialog and change its ID to IDC_PICTURE
  5. Add a Button control to the dialog and change its ID to IDC_SELECT
     
  6. Right-click the Picture Control and click Add Variable...
  7. Create a Control variable named m_Picture and press Enter
    If you don't have pictures, here are a few you can copy and paste somewhere where they will be accessed
     
  8. In the Class View, right-click the name of the dialog class -> Add -> Add Variable...
  9. Add a private CString variable named strPictureName and click Finish
  10. On the dialog box, double-click the Select button and implement its event as follows:
      
    void CFoodPreview1Dlg::OnBnClickedSelect()
{
	// TODO: Add your control notification handler code here
	TCHAR strFilter[] = { TEXT("Picture Files (*.bmp)|*.bmp||") };
	CFileDialog dlg(TRUE, TEXT(".bmp"), NULL, 0, strFilter);

	if( dlg.DoModal() == IDOK )
	{
		strPictureName = dlg.GetFileName();
		Invalidate();
	}

	UpdateData(FALSE);
}
  11. Access the OnPaint event of the dialog box and change it as follows:
      
    void CDialog1Dlg::OnPaint()
{
	CPaintDC dc(this); // device context for painting

	if (IsIconic())
	{
		SendMessage(WM_ICONERASEBKGND,
			    reinterpret_cast<WPARAM>(dc.GetSafeHdc()),
			    0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{
		CDialog::OnPaint();
	}
	
	HBITMAP bmpHandle = (HBITMAP)LoadImage(NULL,
		                               strPictureName,
					       IMAGE_BITMAP,
					       0,
					       0,
					       LR_LOADFROMFILE);
	CBitmap bmpPicture;
	CDC mdcPicture;
	CBitmap *bmpFromHandle = bmpPicture.FromHandle(bmpHandle);

	CRect rctPicture;
	m_Picture.GetWindowRect(&rctPicture);
		
	mdcPicture.CreateCompatibleDC(&dc);
	CBitmap * bmpPrevious = mdcPicture.SelectObject(bmpFromHandle);

	ScreenToClient(&rctPicture);

	dc.BitBlt(rctPicture.left, rctPicture.top,
		  rctPicture.Width(), rctPicture.Height(),
		  &mdcPicture, 0, 0, SRCCOPY);

	dc.SelectObject(bmpPrevious);
	DeleteObject(bmpHandle);
}
  12. Execute the application
     
  13. Close the dialog box

 
 
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