technical-recipes.com

Tag: Bitmaps

  • ‘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

  • Creating Bitmap Files from Raw Pixel Data in C++

    Creating the byte array

    This post describes a means of taking data in the form of raw pixels containing RGB values as well as the image height, width and the number of bits per pixel (24 in this case) and converting this into a bitmap (BMP) file.

    Example Visual Studio 2010 project is downloadable from here:

    www.technical-recipes.com/Downloads/BitmapRawPixels.zip

    In this this post I originally described how I needed a means of representing binary array values (inkjet printhead nozzles turned ON/OFF) as a set of colored ‘squares’ or pixels, so that nozzles switched ON/OFF could be represented by two different colours – black or white. The bitmap width was always going to be 128, while the bitmap length (“SizeValue”) was one of a set of discrete set of values in the range { 1000, 1250, 1251, 1350 }. For this example I did not have to worry about padding additional values (more…)