关于图像划线颜色

Question

1.定义了一个 CDC m_memDC_end2. 对m_memDC_end进行初始设置CClientDC dc(pWnd);
_memDC_end.CreateCompatibleDC(&dc);// by default: MM_TEXT mode
CBitmap bmp;
m_iW_imageOnScreen = m_rect.Width();
m_iH_imageOnScreen = m_rect.Height();
   
bmp.CreateCompatibleBitmap(&dc,m_iW_imageOnScreen,m_iH_imageOnScreen);
m_memDC_end.SelectObject(&bmp);
   
m_penMarker.CreatePen(PS_SOLID,5,RGB(255,0,0)); // Pen for er
m_penConstLine.CreatePen(PS_SOLID,5,RGB(255,100,0)); // Pen 
m_penRed.CreatePen(PS_SOLID,5,RGB(255,0,100)); // Pen for er3.设置了一个左键按下相应代码if (g_bLbuttonDownH)
{
m_memDC_end.SelectObject(&m_penMarker);
m_memDC_end.MoveTo( (g_MousePointH.x*2-30-50-25), (g_MousePointH.y*2-80));
m_memDC_end.LineTo( (g_MousePointH.x*2-30-50-25), (g_MousePointH.y*2+55));//|m_memDC_end.MoveTo( (g_MousePointH.x*2-30+50+25), (g_MousePointH.y*2-80));
m_memDC_end.LineTo( (g_MousePointH.x*2-30+50+25), (g_MousePointH.y*2+55));//|
}
SetStretchBltMode(g_hDC,HALFTONE); 
StretchBlt(g_hDC,0,0,1024,1024,m_memDC_end,0,0,2048,2048,SRCCOPY);注：m_memDC_end是以位图的方式显示图像，并在m_memDC_end划线，但是划线没有彩色的线条，只有深浅，到底是哪里有问题呢？是否还需要BitBlt这个呢？怎么去设置呢？谢谢啦

Answer 1

CClientDC cltDc(this);
CPoint ptOld, ptNew;
CPen pen(PS_SOLID, 1, RGB(255, 0, 0));//设置画笔的颜色
cltDc.SelectObject(&pen); //给ptOld和ptNew赋值,也就是你想划线的2个点的坐标
cltDc.MoveTo(ptOld);
cltDc.LineTo(ptNew);