1. The purpose of the experiment

(1) Grasp the key Bresenham scan conversion algorithm of any slope line segment;

(2) Master the design method of Cline straight line;

(3) Master the programming method of the status bar.

2. Experimental steps

(1) Create MFC application

(2) Define the CLine class

1. Add a handler for message processing

3. Experimental results

Four, experimental experience

In this experiment, through continuous exploration and practice, I learned how to create an MFC application, apply theory to practice, master the design method of straight lines, and learn how to draw arbitrary slopes, although the process is very difficult , Encountered many difficulties, but finally completed the experiment through continuous efforts and gained a lot.

Appendix: Source Code

 CLine.cpp
// The implicit function F(x,y)=y-kx-b, calculate the error term
double CLine::getDistance(double x, double y)
{
	return y - m_k * x - m_b;
}


 // Call MoveTo() of the CDC object to move to the starting point
void CLine::moveTo(CDC *&pDC)
{
	pDC->MoveTo(m_start);
}


 // Use the straight line scanning algorithm to draw a straight line
void CLine::lineTo(CDC *&pDC)
{
	 //If the line is vertical or parallel or k=1
	if ((m_end.x - m_start.x) == 0 || (m_end.y - m_start.y) == 0 ||
		(m_end.x - m_start.x) == (m_end.y - m_end.y) ||
		(m_end.x - m_start.x) == -(m_end.y - m_end.y))
		pDC->LineTo(m_end);
	else
	{
		m_k = ((double)(m_end.y - m_start.y)) / (m_end.x - m_start.x);
		m_b = m_start.y - m_k * m_start.x;
		if (0 < m_k && m_k < 1)
			kOne(pDC);
		else if (m_k > 1)
			kTwo(pDC);
		else if (-1 < m_k && m_k < 0)
			kThree(pDC);
		else if (m_k < -1)
			kFour(pDC);
	}
}


 // Set the starting point of the straight line
void CLine::setStartPoint(CPoint point)
{
	this->m_end = point;
}


 // Set the end point of the straight line
void CLine::setEndPoint(CPoint point)
{
	this->m_start = point;
}


 // The slope of the drawn line is in the range of 0<k<1
void CLine::kOne(CDC *&pDC)
{
	 //Always keep the starting point X coordinate less than Y coordinate
	if (m_start.x > m_end.x)
	{
		CPoint tmp = m_start;
		m_start = m_end;
		m_end = tmp;
	}
	double d = 0;
	 COLORREF color = RGB(0, 0, 0); //Set the color of the straight line
	 CPoint next = m_start; //Record starting point
	 pDC->SetPixelV(next, color); //Draw starting point
	for (int i = m_start.x + 1; i <= m_end.x; i++)
	{
		 next.x++; //The X axis is the main displacement direction
		 if (d <= 0) //The straight line is above the midpoint error
			 next.y++; //take the point above
		 pDC->SetPixelV(next, color); //Draw points
		 d = getDistance((double)next.x + 1, next.y + 0.5); //Next midpoint
	}
}


 // The slope of the drawn line is in the range of k>1
void CLine::kTwo(CDC *&pDC)
{
	if (m_start.y > m_end.y)
	{
		CPoint tmp = m_start;
		m_start = m_end;
		m_end = tmp;
	}
	double d = 0;
	COLORREF color = RGB(0, 0, 0);
	CPoint next = m_start;
	pDC->SetPixelV(next, color);
	for (int i = m_start.y + 1; i <= m_end.y; i++)
	{
		next.y++;
		if (d > 0)
			next.x++;
		pDC->SetPixelV(next, color);
		d = getDistance(next.x + 0.5, (double)next.y + 1);
	}
}


 // The slope of the drawn line is in the range of -1<k<0
void CLine::kThree(CDC *&pDC)
{
	if (m_start.x < m_end.x)
	{
		CPoint temp = m_start;
		m_start = m_end;
		m_end = temp;
	}
	double d = 0;
	COLORREF color = RGB(0, 0, 0);
	CPoint next = m_start;
	pDC->SetPixelV(next, color);
	for (int i = m_start.x - 1; i >= m_end.x; i--)
	{
		next.x--;
		if (d < 0)
			next.y++;
		pDC->SetPixelV(next, color);
		d = getDistance((double)next.x - 1, next.y + 0.5);
	}
}


 // The slope of the drawn line is in the range of k<-1
void CLine::kFour(CDC *&pDC)
{
	if (m_start.y < m_end.y)
	{
		CPoint tmp = m_start;
		m_start = m_end;
		m_end = tmp;
	}
	double d = 0;
	COLORREF color = RGB(0, 0, 0);
	CPoint next = m_start;
	pDC->SetPixelV(next, color);
	for (int i = m_start.y - 1; i >= m_end.y; i--)
	{
		next.y--;
		if (d < 0)
			next.x++;
		pDC->SetPixelV(next, color);
		d = getDistance(next.x + 0.5, (double)next.y - 1);
	}
}
 Message handler:
 Left mouse button down
 Release the left mouse button
 Display coordinates when the mouse moves:
void CMFCApplication1View::OnLButtonDown(UINT nFlags, CPoint point)
{
	 // The starting point of the record when the mouse is pressed
	this->line.setStartPoint(point);
	CView::OnLButtonDown(nFlags, point);
}


void CMFCApplication1View::OnLButtonUp(UINT nFlags, CPoint point)
{
	 // Release the mouse to record the end point
	this->line.setEndPoint(point);
	CDC *pDC = GetDC();
	this->line.moveTo(pDC);
	this->line.lineTo(pDC);
	CView::OnLButtonUp(nFlags, point);
}


void CMFCApplication1View::OnMouseMove(UINT nFlags, CPoint point)
{
	 // TODO: Add message handler code and/or call default value here
	CString stringX, stringY;
	CMainFrame * pFrame = (CMainFrame *)AfxGetMainWnd();
	CMFCStatusBar * pStatus = &pFrame->m_wndStatusBar;
	if (pStatus != NULL)
	{
		 //_T is a macro, the function is to make your program support Unicode encoding (double-byte encoding)
		stringX.Format(_T("x=%d"), point.x);
		stringY.Format(_T("y=%d"), point.y);

		CClientDC dc(this);
		CSize sizeX = dc.GetTextExtent(stringX);
		CSize sizeY = dc.GetTextExtent(stringY);
		pStatus->SetPaneInfo(1, nFlags, SBPS_NORMAL, sizeX.cx);
		pStatus->SetPaneText(1, stringX);
		pStatus->SetPaneInfo(2, nFlags, SBPS_NORMAL, sizeY.cx);
		pStatus->SetPaneText(2, stringY);

	}
	CView::OnMouseMove(nFlags, point);
}