绘制直线

void drawLine(int x1,int y1,int x2,int y2,UINT color)
{
    int dx = x2 - x1;
    int dy = y2 - y1;
    int ux = ((dx > 0) << 1) - 1;//x的增量方向,取1或-1
    int uy = ((dy > 0) << 1) - 1;//y的增量方向,取1或-1

    dx = abs(dx);
    dy = abs(dy);

    int x = x1, y = y1;
    int eps = 0;

    //线段靠近x轴
    if(dx > dy)
    {
        for (x = x1;x != x2 + ux;x += ux)
        {
            setPixels(x, y, color);
            eps += dy;
            if((eps << 1) >= dx)
            {
                y += uy;
                eps -= dx;
            }
        }
    }
    else
    {
        for (y = y1; y != y2 + uy; y += uy)
        {
            setPixels(x, y, color);
            eps += dx;
            if ((eps << 1) >= dy)
            {
                x += ux;
                eps -= dy;
            }
        }
    }
}