RE: [GD-Windows] In memory bitmap to HBITMAP

[Jon W. <hp...@mi...>]

Here's my personal utility offscreen bitmap generation function:

void
MyBitmap::setSize( 
  int width, 
  int height
  )
{
  assert( !bitmap );  //  can't re-allocate bitmap once done
  assert( !bits );
  xSize = width;
  ySize = height;
  dc = gl->getUtilDC( );
  BITMAPINFOHEADER bmi;
  memset( &bmi, 0, sizeof( bmi ) );
  bmi.biSize = sizeof( bmi );
  bmi.biWidth = width;
  bmi.biHeight = height;
  bmi.biPlanes = 1;
  bmi.biBitCount = 32;
  bmi.biCompression = BI_RGB;
  bitmap = CreateDIBSection( dc, (BITMAPINFO *)&bmi, DIB_RGB_COLORS, (void **)&bits, 0, 0 );
  assert( bitmap != 0 );
  assert( bits != 0 );
  textColor = 0xffffff;
  bgColor = 0;
  fillRect( 0, 0, width, height, 0 );
}

getUtilDC() returns a DC previously returned from CreateCompatibleDC().

fillRect() draws into the bitmap as such:

void 
MyBitmap::fillRect( 
  int left, 
  int top, 
  int width, 
  int height, 
  unsigned int pixel
  )
{
  assert( bitmap );
  assert( dc );
  HBITMAP oldBitmap = (HBITMAP)SelectObject( dc, bitmap );
  HBRUSH b = CreateSolidBrush( MK_COLORREF(pixel) );
  RECT r;
  r.left = left;
  r.top = top;
  r.right = left+width;
  r.bottom = top+height;
  BOOL res = FillRect( dc, &r, b );
  assert( res );
  SelectObject( dc, oldBitmap );
  DeleteObject( b );
  dirty = true;
}

Hope this helps.

Cheers,

			/ h+


> -----Original Message-----
> From: gam...@li...
> [mailto:gam...@li...]On Behalf Of
> Brian Hook
> Sent: Thursday, December 06, 2001 6:04 PM
> To: gam...@li...
> Subject: [GD-Windows] In memory bitmap to HBITMAP
> 
> 
> I'm struggling with something fairly basic -- I want to load a BMP out
> of a compressed file, convert to an HBITMAP, then blit it into a DDraw
> surface.  I know how to do the first and last part, but the middle is
> causing problems.  Even worse, I'm not getting any errors.
> 
> Loading the bitmap doesn't seem to be a problem.  I load it up and parse
> and find the BITMAPFILEHEADER and BITMAPINFOHEADER no probs.  I also
> locate the raw bits no problem (and inspect with the debugger to make
> sure I'm getting what I think I'm getting -- in this case, solid
> magenta).  Looks fine.
> 
> The next step is to create a DC compatible with the desktop:
> 
> HDC hDC = CreateCompatibleDC( NULL );
> 
> I then create a HBITMAP compatible with DC, and using the bits I pulled:
> 
> HBITMAP hbm;
> 
> hbm = CreateDIBitmap( hDC, lpBMIH, CBM_INIT, lpBits, lpBMIH,
> DIB_RGB_COLORS );
> 
> lpBMIH are simply pointers to the appropriate BITMAPINFOHEADER.  They
> have correct values in them.  The bitmap is returned successfully.
> 
> To verify things, I grab the bits out of the Bitmap to make sure
> everything is cool:
> 
> GetDIBits( hDC, hbm, 0, iHeight, tempbuffer, &bmi, DIB_RGB_COLORS );
> 
> It returns the correct number of scan lines, but tempbuffer is filled
> with black.  This means either the CreateDIBitmap() filled in the bitmap
> with black, or the GetDIBits() failed somehow.  I can't figure out which
> is the real culprit, but the bitmap is pretty much a black square.
> 
> Any suggestions on how to hunt this down?
> 
> 
> 
> 
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