扫描线填充算法,单链表实现

扫描线填充算法

typedef struct ET{    float x;    float dx;    float ymax;    ET* next;}NET,AET;

建立NET表

//等间距且为i=1的扫描线    for (int i = 0; i < Ymax; i++)    {        //pNET[i] ->next = NULL;        for (int j = 0; j < numofpoint; j++)        {            if (polypoint[j].y == i)            {                NET *rear = pNET[i];                //设置尾指针                if (polypoint[(j - 1 + numofpoint) % numofpoint].y>polypoint[j].y)                {                    NET *p1 = new NET;                    p1->x = polypoint[j].x;         //                    p1->dx = (polypoint[(j - 1 + numofpoint) % numofpoint].x - polypoint[j].x) / (polypoint[(j - 1 + numofpoint) % numofpoint].y - polypoint[j].y);                         p1->ymax = polypoint[(j - 1 + numofpoint)%numofpoint].y;                    //表头插入法                    //p1->next = pNET[i]->next;     //将将待插入的节点的后置节点指向头结点后的节点                    //pNET[i]->next = p1;           //将头结点的后置节点指向新节点，即新节点连到表头                    //表尾插入法                    rear->next = p1;                //将新节点连到链尾                    rear = p1;                      //尾指针后移                    rear->next = NULL;              //链表最后的尾节点的后继指针置空                }                if (polypoint[(j + 1 + numofpoint) % numofpoint].y>polypoint[j].y)                {                    NET *p2 = new NET;                    p2->x = polypoint[j].x;                    p2->dx = (polypoint[j].x - polypoint[(j + 1 + numofpoint) % numofpoint].x) / (polypoint[j].y - polypoint[(j + 1 + numofpoint) % numofpoint].y);                    p2->ymax = polypoint[(j + 1 + numofpoint) % numofpoint].y;                    //表头法                    //p2->next = pNET[i]->next;                    //pNET[i]->next = p2;                    //表尾法                    rear->next = p2;                    rear = p2;                    rear->next = NULL;                }            }        }    }

建立AET表

    //标记NET的Ymin，并使得AET从这开始。    for (int i = 0; i <= Ymax; i++)    {        if (pNET[i]->next!=NULL)        {            Ymin = i;            break;        }    }    //NET转换为AET    for (int i = Ymin; i <= Ymax; i++)    {        NET *np = pNET[i]->next;        //AET* ap = new AET;        //ap->next = NULL;        //把NET表中y类结点非空的数据移入AET        while (np)        {            AET *p = new AET;            p->x = np->x;            p->dx = np->dx;            p->ymax = np->ymax;            p->next = pAET[i]->next;            pAET[i]->next= p;            np = np->next;        }        //首先考虑是否有与多边形的新交点，通过前射线的x+dx判断。        AET *ap = pAET[i-1]->next;        while (ap)        {            AET *p = new AET;            p->x = ap->x + ap->dx;            p->dx = ap->dx;            p->ymax = ap->ymax;            if (p->ymax == i)   //当ymax == Y时,舍去这个点。因为每条边被看作下闭上开的            {                delete p;            }            else            {                p->next = pAET[i]->next;                pAET[i]->next = p;            }            ap = ap->next;        }

AET表还未排序

AET* InsertSort(AET*& head){    if (head ==NULL)    {        return head;    }    AET* pmax = head;    //第一次指向第二个元素      AET* work = head->next;    while (work)    {        // 将work插入到head位置          if (work->x < head->x)        {            pmax->next = work->next;            work->next = head;            head = work;        }        else if (work->x == head->x)        {            if (work->dx < head->dx)            {                pmax->next = work->next;                work->next = head;                head = work;            }        }        // 将数据插入到中间          else if (work->x > head->x && work->x < pmax->x)        {            AET* bg = head;            AET* pre = NULL;            while (bg && bg->x < work->x )            {                pre = bg;                bg = bg->next;            }            if (bg->x == work->x)            {                pre = bg;                bg = bg->next;            }            pmax->next = work->next;            work->next = bg;            pre->next = work;        }        else            pmax = work;                    //直接前移          work = pmax->next;    }    return head;}

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