点_直线沿着平行线_垂直线各自扩展

typedef struct _GFPoint
{
    float x;
    float y;
}GFPoint;

typedef struct _GFPolyline
{
    uint32_t count;
    GFPoint * pPoints;
} GFPolyline;

/**
 * @brief 指定点沿着平行于指定直线的方向移动指定距离后获得的新点
 * @param[in] pStart - 起始方向点
 * @param[in] pEnd - 终止方向点
 * @param[in] pPoint - 指定点 【可以是直线上的点或者不是】
 * @param[in] dDis - 移动的距离
 * @return 返回移动后的点
 */

GFPoint GetPointAlongLine(GFPoint pStart, GFPoint pEnd, GFPoint pPoint, double dDis);

/**
 * @brief 直线起始点各向外扩展指定距离【平行于该直线】
 * @param[in] pGFPolyline - 直线起始距离
 * @param[in] dDis - 移动的距离
 * @return void
 */
void GFPolylineExtendPoints(GFPolyline * pGFPolyline, double dDis);

/**
 * @brief 指定点沿着垂直于指定直线的方向移动指定距离后获得的新点
 * @param[in] pStart - 起始方向点
 * @param[in] pEnd - 终止方向点
 * @param[in] pPoint - 指定点 【可以是直线上的点或者不是】
 * @param[in] dLen - 线宽
 * @param[in] dDis - 移动的距离
 * @return 返回移动后的点
 * @note 调用约定:
 * 1. dLen - 【如果多次调用该接口，而线宽又不改变的情况下，可以外部算一次，作为参数；否则传-1.
 * 2. dDis - 距离的正负代表了扩充点在线的左边还是右边. 正 - 代表在以线的起始点为方向的右边，反之；
 */

GFPoint GetPointVerticalToLine(GFPoint pStart, GFPoint pEnd, GFPoint pPoint, double dLen, double dDis);

/**
 * @brief 直线起始点沿着垂直于该直线的方向外扩展指定距离
 * @param[in] pPolyline - 直线起始距离
 * @param[in] width - 线宽
 * @param[out] pGFPointStartl, pGFPointStartr - 线起点按照指定宽度扩充后的线左右两个点
 * @param[out] pGFPointEndl, pGFPointEndr - 线终点按照指定宽度扩充后的线左右两个点
 * @return void
 */
void GFPolylineExternsPoints(const GFPolyline * pGFPolyline, float width,
                             GFPoint * pGFPointStartr, GFPoint * pGFPointStartl,
                             GFPoint * pGFPointEndr, GFPoint * pGFPointEndl);


GFPoint GetPointAlongLine(GFPoint pStart, GFPoint pEnd, GFPoint pPoint, double dDis)
{
    GFPoint pP;
    double dLen = 0;

    dLen = hypot(pEnd.x - pStart.x, pEnd.y - pStart.y);
    assert(0 != dLen);
    pP.x = pPoint.x + (pEnd.x - pStart.x) * (dDis/dLen);
    pP.y = pPoint.y + (pEnd.y - pStart.y) * (dDis/dLen);

    return pP;
}

void GFPolylineExtendPoints(GFPolyline * pGFPolyline, double dDis)
{
    GFPoint rGFPointEx, lFGPointEx; ///< 延伸后的点

    if (NULL == pGFPolyline || NULL == pGFPolyline->pPoints)
    {
        return;
    }

    lFGPointEx = GetPointAlongLine(pGFPolyline->pPoints[1], pGFPolyline->pPoints[0], pGFPolyline->pPoints[0], dDis);

    pGFPolyline->pPoints[0].x = lFGPointEx.x;
    pGFPolyline->pPoints[0].y = lFGPointEx.y;

    if (2 == pGFPolyline->count)
    {
        rGFPointEx = GetPointAlongLine(pGFPolyline->pPoints[0], pGFPolyline->pPoints[1], pGFPolyline->pPoints[1], dDis);
    }
    else
    {
        rGFPointEx = GetPointAlongLine(pGFPolyline->pPoints[pGFPolyline->count - 2], pGFPolyline->pPoints[pGFPolyline->count - 1], pGFPolyline->pPoints[pGFPolyline->count - 1], dDis);
    }
    pGFPolyline->pPoints[1].x = rGFPointEx.x;
    pGFPolyline->pPoints[1].y = rGFPointEx.y;
}

GFPoint GetPointVerticalToLine(GFPoint pStart, GFPoint pEnd, GFPoint pPoint, double dLen, double dDis)
{
    GFPoint pP;

    if (-1 == dLen)
    {
        dLen = hypot(pEnd.x - pStart.x, pEnd.y - pStart.y);
        assert(0 != dLen);
    }


    pP.x = pPoint.x - (pEnd.y-pStart.y) * (dDis/dLen);
    pP.y = pPoint.y + (pEnd.x-pStart.x) * (dDis/dLen);

    return pP;
}

void GFPolylineExternsPoints(const GFPolyline * pGFPolyline, float width,
                             GFPoint * pGFPointStartr, GFPoint * pGFPointStartl,
                             GFPoint * pGFPointEndr, GFPoint * pGFPointEndl)
{
    double dLen = 0;
    if (NULL == pGFPolyline || pGFPolyline->count < 2)
    {
        return;
    }

    width /= 2;

    dLen = hypot((pGFPolyline->pPoints[1].x - pGFPolyline->pPoints[0].x), (pGFPolyline->pPoints[1].y - pGFPolyline->pPoints[0].y));
    *pGFPointStartr = GetPointVerticalToLine(pGFPolyline->pPoints[0], pGFPolyline->pPoints[1], pGFPolyline->pPoints[0], dLen, width);
    *pGFPointStartl = GetPointVerticalToLine(pGFPolyline->pPoints[0], pGFPolyline->pPoints[1], pGFPolyline->pPoints[0], dLen, -width);

    ///< 考虑到线是折线，而我们只需要起始点进行扩展
    if (2 == pGFPolyline->count)
    {
        *pGFPointEndr = GetPointVerticalToLine(pGFPolyline->pPoints[0], pGFPolyline->pPoints[1], pGFPolyline->pPoints[1], dLen, width);
        *pGFPointEndl = GetPointVerticalToLine(pGFPolyline->pPoints[0], pGFPolyline->pPoints[1], pGFPolyline->pPoints[1], dLen, -width);
    }
    else
    {
        dLen = hypot((pGFPolyline->pPoints[pGFPolyline->count - 1].x - pGFPolyline->pPoints[pGFPolyline->count - 2].x), (pGFPolyline->pPoints[pGFPolyline->count - 1].y - pGFPolyline->pPoints[pGFPolyline->count - 2].y));
        *pGFPointEndr = GetPointVerticalToLine(pGFPolyline->pPoints[pGFPolyline->count - 2], pGFPolyline->pPoints[pGFPolyline->count - 1], pGFPolyline->pPoints[pGFPolyline->count - 1], dLen, width);
        *pGFPointEndl = GetPointVerticalToLine(pGFPolyline->pPoints[pGFPolyline->count - 2], pGFPolyline->pPoints[pGFPolyline->count - 1], pGFPolyline->pPoints[pGFPolyline->count - 1], dLen, -width);
    }
}