Re: Copying Bitmap

=?Utf-8?B?Q2hhcmxlcyBUYW0=?= <>
Sun, 3 Jun 2007 19:51:01 -0700
Thanks for your inputs, the updated function is shown below.
Unfortunately, this function doesn't work when it is called by a timer and
the source window area is obscured by another application. Under this
situation, the target's contents includes a partial source and the other
application window area.
Do you know how it should be corrected?

void CopyWindowAreaToStaticAndBitmap(CDC& dc_source, CStatic& cs_target,
CBitmap& bitmap_output, bool& bitmap_output_valid)
  bitmap_output_valid = false;

  CRect rc_static;
  cs_target.GetClientRect( rc_static );

  bitmap_output.CreateCompatibleBitmap( &dc_source, rc_static.Width(),
rc_static.Height() );

  // Copy source onto output bitmap
  CDC dc_bitmap;
  dc_bitmap.CreateCompatibleDC( &dc_source );
  dc_bitmap.SelectObject( &bitmap_output );
  dc_bitmap.BitBlt( 0, 0, rc_static.Width(), rc_static.Height(), &dc_source,
0, 0, SRCCOPY );

  // Copy output bitmap onto display target
  CClientDC dc_target( &cs_target );
  dc_target.BitBlt( 0, 0, rc_static.Width(), rc_static.Height(), &dc_bitmap,
0, 0, SRCCOPY );

"Ashot Geodakov" wrote:

Here's what should work for you:

void CMyDlg::CopyWindowAreaToStatic( CDC& cdc )
    // First copy a screen area to a compatible DC/Bitmap.
    CDC dcCompatible;
    dcCompatible.CreateCompatibleDC( &cdc );
    CBitmap bitmap;
    bitmap.CreateCompatibleBitmap( &cdc, 200, 200 ); // Change the width and
height to desired ones.
    dcCompatible.SelectObject( &bitmap );
    dcCompatible.BitBlt( 0, 0, 200, 200, &cdc, 0, 0, SRCCOPY );

    // This is to test that dcCompatible indeed has the right bits in it.
    CClientDC dcStatic( &m_picture );
    dcStatic.BitBlt( 0, 0, 200, 200, &dcCompatible, 0, 0, SRCCOPY );

    // This is to test if bitmap has the correct bits in it.
    BYTE bits[200 * 200 * 4]; // Assuming there's 4 bytes per pixel.
    bitmap.GetBitmapBits( 200 * 200 * 4, bits );
    // You may append these bits to a correct bitmap file headers and save
it as a .BMP file.

Make this bitmap a class member if you want to re-use it in painting
procedures. But add bitmap.DeleteObject() at the beginning of this function.

Hope it helps...

"Charles Tam" <> wrote in message

I've tried your approach and it's working very well. Thanks.
Could you help me to extend the function to return a CBitmap copy of the
source image? Is the correct way (see below)?

void CMyDlg::CopyWindowAreaToStatic( CDC& cdc, CBitmap& bm_copy )
   CClientDC dcStatic( &m_picture );
   CRect rcStatic;
   m_picture.GetClientRect( rcStatic );
   dcStatic.BitBlt( 0, 0, rcStatic.Width(), rcStatic.Height(), &cdc, 0, 0,
   bm_copy.CreateCompatibleBitmap( cdc, rsStatic.Width(),

"Ashot Geodakov" wrote:

Create a sample MFC dialog app.

On the dialog place two buttons, "Copy Window" and "Copy Client".
Also place a static Image control and create its corresponding variable
m_picture in the dialog class. Using Wizard, it'll generate something

CStatic m_picture;

in the dialog definition.

Define the following function in the dialog:

void CMyDlg::CopyWindowAreaToStatic( CDC& cdc )
    CClientDC dcStatic( &m_picture );
    CRect rcStatic;
    m_picture.GetClientRect( rcStatic );
    dcStatic.BitBlt( 0, 0, rcStatic.Width(), rcStatic.Height(), &cdc, 0,

Handle two button clicks for Copying window and client area:

void CMyDlg::OnBnClickedButtonwindow()
    // TODO: Add your control notification handler code here
    CopyWindowAreaToStatic( CWindowDC( this ) );

void CMyDlg::OnBnClickedButtonclient()
    // TODO: Add your control notification handler code here
    CopyWindowAreaToStatic( CClientDC( this ) );


"Charles Tam" <> wrote in message

I'm trying to copy the bitmap onto a CStatic object for display
insteads of the clipboard. Unfortunately, I cannot got it to work.
could I correct it?

CDC dc;
HDC hdc;
hdc = ::GetWindowDC(this->m_hWnd);

CDC memDC;

CBitmap bm;
CRect r;

CString s;
CSize sz(r.Width(), r.Height());
CBitmap * oldbm = memDC.SelectObject(&bm);
memDC.BitBlt(0, 0,,, &dc, 0, 0, SRCCOPY);

m_copy.SetBitmap(bm); // display the bitmap onto a CStatic object

::ReleaseDC(this->m_hWnd, dc.Detach());

"Ashot Geodakov" wrote:

There are also nice classes like CWindowDC and CClientDC available,
through all this Attach(), Detach() and ReleaseDC() ?

"Charles Tam" <> wrote in message

Hi Joseph, I've tried your code
in an example MFC app (VS6 C++).

Unfortunately, the compiler has returned an error on the line
"::ReleaseDC(dc.Detach());" with an error message of "error C2660:
'ReleaseDC' : function does not take 1 parameters".
Could you please tell me how to correct it?

"Joseph M. Newcomer" wrote:

It captures whatever pixels are on the screen.

On Fri, 1 Jun 2007 11:43:01 -0700, Charles Tam

Thanks for your reply and reference information.
I've another question on screen capturing.

For example, my MFC app contains a Windows Media Player ActiveX
is displaying a video session. Could I try out your screen
technique to copy the current video frame on the control into a

"Joseph M. Newcomer" wrote:

Depends on how the data is created and whether or not all
is displayed on the

For example, see my essay on Screen Capture on my MVP Tips site.
this only works if
the image contains everything you need to see, and is not
other windows. If
the actual image is is larger, then what you would have to do is
create a memory DC,
select a bitmap into it, and then call your OnDraw handler to
into the bitmap. The
catch here is that you have to know how large to make the
which means that you
will somehow have to track this. One way to handle this is to
call OnDraw with the
default (one-pixel) bitmap and track the largest physical pixel
coordinate you write
(taking into account mapping modes), then create a bitmap, call
again, only this
time with a correctly-sized correct-color-depth bitmap selected
Unless you have an
independent way to compute the bitmap size, this may be the only
solution that works.

On Thu, 31 May 2007 23:55:00 -0700, Charles Tam

I've a CWnd derived class e.g. CWMPPlayer4.

How do I copy the current displayed data from the CMPPlayer4
into a
CBitmap object?

Joseph M. Newcomer [MVP]
MVP Tips:

Joseph M. Newcomer [MVP]
MVP Tips:

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