CreateRegionFromFile

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• Download source - 21.5 Kb

Introduction

This very simple function creates a region from a bitmap (.bmp) file. 8, 16, 24 and 32 bit color modes are supported.

The function takes two parameters:

• hBmp - a handle to the bitmap image.
• color - transparent color.

HRGN CreateRgnFromFile( HBITMAP hBmp, COLORREF color );

Using the function is very simple. For example, if you wish to set the window shape of your dialog, then in your OnInitDialog handler, do this:

BOOL CFileRgnDlg::OnInitDialog()
{
    CDialog::OnInitDialog();

    // load image
    HBITMAP hBmp = (HBITMAP)LoadImage( AfxGetInstanceHandle(), 
                     "Rgn.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE );
    // if fail - nothing to do
    if ( hBmp == NULL ) return TRUE;
    // create region, let the RED color be transparent

    HRGN hRgn = CreateRgnFromFile( hBmp, RGB(255,0,0) );

    // build memory dc for background
    CDC* dc = GetDC();
    m_dcBkGrnd = CreateCompatibleDC( dc->m_hDC );
    ReleaseDC( dc );
    // select background image
    SelectObject( m_dcBkGrnd, hBmp );
    // set window size the same as image size
    SetWindowPos( NULL, 0, 0, m_dwWidth, m_dwHeight, 
                           SWP_NOZORDER | SWP_NOMOVE );
    // assign region to window
    SetWindowRgn( hRgn, FALSE );

    return TRUE;
}

History

• December 08 2001

  * cut & paste bug for 16-bit mode (white color as transparent did not work).

  * pixels in a last column has not been used.

  + Now you can use non-aligned (by width) images.

• June 11 2001

  * ExtCreateRegion NT-problem (personal thanks to Martin for reporting about it).