Learning OpenCV, 2nd Edition

0, 0,

bmi.bmiHeader.biWidth, abs(bmi.bmiHeader.biHeight),

m_bitmapBits,

&bmi,

DIB_RGB_COLORS,

SRCCOPY

);

} else {

dc.FillRect(rect, COLOR_WINDOW);

}

return 0;

}

LRESULT COpenCVTestView::OnTimer(

UINT /*uMsg*/,

WPARAM /*wParam*/,

LPARAM /*lParam*/,

BOOL& /*bHandled*/

) {

// Nothing to do if capture object is not open

//

if( !m_cap.isOpened() ) return 0;

m_cap.read( m_cv_img );

_copyImage();

Invalidate();

return 0;

}

LRESULT COpenCVTestView::OnEraseBkgnd(

UINT /*uMsg*/,

WPARAM /*wParam*/,

LPARAM /*lParam*/,

BOOL& /*bHandled*/

) {

// since we completely paint our window in the OnPaint handler, use

// an empty background handler

return 0;

}

This code illustrates how to use bitmap-based drawing in a C++ application under Windows. This method

is simpler, but less efficient than using DirectShow to handle the video stream.

If you are using the .NET Runtime (either through C#, VB.NET or Managed C++), then

you may want to look into a package that completely wraps OpenCV, such as Emgu

(http://emgu.com).

Drawing Things

We often want to draw some kind of picture, or to draw something on top of an image obtained from

somewhere else. Toward this end, OpenCV provides a menagerie of functions that will allow us to make

lines, squares, circles, and the like.

The drawing functions available will work with images ...