void CCGPainterView::DrawLine(CDC *pDC, CPoint ptStartPoint, CPoint ptEndPoint, COLORREF cLineColor)
{
/*************************************************************
 write the Bresenham' line algorithm for drawing the line
 use function: pDC->SetPixelV(point, cLineColor); to drawing a pixel
编码直线生成算法，调用函数pDC->SetPixelV(point, cLineColor)画像素。
*************************************************************/
    //Bresenham算法
    int x0 = ptStartPoint.x, y0 = ptStartPoint.y;
    int xEnd = ptEndPoint.x, yEnd = ptEndPoint.y;
    int dx = xEnd - x0;
    int dy = yEnd - y0;
    int converse = 0;
    int dxabs = fabs(dx);
    int dyabs = fabs(dy);
    int s1 = xEnd > x0 ? 1 : -1;
    int s2 = yEnd > y0 ? 1 : -1;
    int x = x0, y = y0;
    if (dyabs > dxabs)
    {
        int tmp = dxabs;
        dxabs = dyabs;
        dyabs = tmp;
        converse = 1;
    }
    int p = 2 * dyabs - dxabs;
    for (int i = 0; i < dxabs; i++)
    {
        CPoint point(x, y);
        pDC->SetPixelV(point, cLineColor);
        if (p >= 0)
        {
            if (converse)
            {
                x += s1;
            }
            else
            {
                y += s2;
            }
            p -= 2 * dxabs;
        }
        if (converse)
        {
            y += s2;
        }
        else
        {
            x += s1;
        }
        p += 2 * dyabs;
    }
}