Question

c++ GDI +图像问题

void Ctest1View::OnMouseMove(UINT nFlags, CPoint point)
{

if(flag == true)
{
CDC *dc = GetDC();
Graphics m_Graphics(dc->m_hDC);
Pen m_pen(Color(255,0,0));
m_Graphics.Clear(Color(255,255,255));

m_Graphics.DrawLine(&m_pen,m_Oldpt.x,m_Oldpt.y,point.x,point.y);
m_Origin = point;
}

CView::OnMouseMove(nFlags, point);
}
void Ctest1View::OnLButtonDown(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
flag = true;
m_Origin = m_Oldpt = point;

CView::OnLButtonDown(nFlags, point);
}

我的线一画出来就被清了 我想知道怎么保存

Answer 1

把绘图的代码放到OnDraw函数里。OnDraw函数头里有dc指针，不用GetDC的。