‘Blitting’ a Bitmap Image to the Screen.

I recently needed to revisit this to create simple monochrome bitmaps representing the sets of nozzles turned off/on on a Xaar microarrayer printhead.

Sample code here.  Essential steps are outlined in the following code

// 1. Create the uninitialized bitmap, that is compatible
// with the the specified device context
CPaintDC dc( this );
CBitmap bitmap;
bitmap.CreateCompatibleBitmap( &dc, 20, 20 );

// 2. Create memory device context, that is compatible
// with the specified device (dc in this case)
CDC dcMem;
dcMem.CreateCompatibleDC( &dc );

// 3. Obtain/create the bitmap and select into
// the memory device context.
CBrush brushblue( RGB( 0, 0, 255 ) );
CBrush brush( RGB( 0, 255, 255 ) );
CBitmap* pOldBitmap = dcMem.SelectObject( &bitmap );
dcMem.FillRect( CRect( 0, 0, 10, 10 ), &brushblue );
dcMem.FillRect( CRect( 10, 0, 20, 10 ), &brush );
dcMem.FillRect( CRect( 0, 10, 10, 20 ), &brush );
dcMem.FillRect( CRect( 10, 10, 20, 20 ), &brushblue );

// 4. Obtain the bitmap dimensions in pixels, making sure
// they are then mapped into their corresponding logical
// units
BITMAP bm;
bitmap.GetBitmap( &bm );
CPoint size( bm.bmWidth, bm.bmHeight );
CPoint org( 0, 0 );
dc.DPtoLP( &size );
dc.DPtoLP( &org );     

// 5. Specify the memory device context’s mapping mode:
// MM_ANISOTROPIC,  MM_HIENGLISH etc
dcMem.SetMapMode( dc.GetMapMode() );

// 6. ‘Blit’ the rectangular block of pixel data from
// the source device context (dcMem) to the destination
// device context (dc)
dc.BitBlt( 12,
           12,
           size.x,
           size.y,
           &dcMem,
           org.x,
           org.y,
           SRCCOPY );

// 7. Restore the default bitmap
dcMem.SelectObject( pOldBitmap );

A simple dialog application example to download:    Bitmaps.zip

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