计算机图形学_有效边表算法源代码

#include <stdio.h>#include <malloc.h>#include <gl/glut.h>#include <Windows.h>#define EPSILON 0.000001 //最小浮点数//点结构体struct Point{int x; //x坐标int y; //y坐标};//线结构体struct Line{Point high_point; //高端点Point low_point; //低端点int is_active; //是否为有效边，水平边（0），非水平边（1）double inverse_k; //斜率k的倒数};//边结点struct EdgeNode{double x; //扫描线与边交点的x坐标（边的低端点的x坐标）int y_max; //边的高端点的y坐标ymaxdouble inverse_k; //斜率k的倒数EdgeNode *next; //下一个边结点的指针};//有效边表struct ActiveEdgeTable{int y; //扫描线yEdgeNode *head; //边链表的头指针};//桶结点typedef struct Bucket{int y; //扫描线yEdgeNode *head; //边链表的头指针Bucket *next; //下一个桶的指针} EdgeTable;int compare(Point p1, Point p2);Line* create_lines(Point points[], int n);Point get_lowest_point(Line lines[], int n);Point get_highest_point(Line lines[], int n);void swap(Line &l1, Line &l2);void sort(Line lines[], int n);EdgeTable* create_edge_table(Line lines[], int n);ActiveEdgeTable* init_active_table(EdgeTable *edge_table);void delete_edge(ActiveEdgeTable *active_table, int y_max);void add_edge(ActiveEdgeTable *active_table, EdgeNode edge);ActiveEdgeTable* update_active_table(ActiveEdgeTable *active_table, EdgeTable *edge_table);void DrawPolygon(Point points, int n);void DrawGrid(int x, int y);void Fill(Point points[], int n);void Initial();void Display();int main(int argc, char* argv[]){glutInit(&argc, argv);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);glutInitWindowSize(400, 300);glutInitWindowPosition(100, 120);glutCreateWindow("Polygon Filling");glutDisplayFunc(Display);Initial();glutMainLoop();return 0;}//比较2个点的高度int compare(Point p1, Point p2){if (p1.y > p2.y)return 1;else if (p1.y == p2.y)return 0;return -1;}//由点数组生成线段数组Line* create_lines(Point points[], int n){Line *lines = (Line*)malloc(n * sizeof(Line));for (int i = 0; i < n; ++i){Point p1 = points[i];Point p2 = points[(i + 1) % n];int result = compare(p1, p2);if (result == 0)lines[i].is_active = 0;elselines[i].is_active = 1;lines[i].high_point = result > 0 ? p1 : p2;lines[i].low_point = result < 0 ? p1 : p2;lines[i].inverse_k = (double)(p2.x - p1.x) / (double)(p2.y - p1.y);}return lines;}//获取线数组中最低的端点Point get_lowest_point(Line lines[], int n){Point lowest_point = lines[0].low_point;for (int i = 1; i < n; ++i){Point low_point = lines[i].low_point;if (compare(lowest_point, low_point) > 0)lowest_point = low_point;}return lowest_point;}//获取线数组中最高的端点Point get_highest_point(Line lines[], int n){Point highest_point = lines[0].high_point;for (int i = 1; i < n; ++i){Point high_point = lines[i].high_point;if (compare(highest_point, high_point) < 0)highest_point = high_point;}return highest_point;}//交换2个Line对象void swap(Line &l1, Line &l2){Line temp = l1;l1 = l2;l2 = temp;}//对线数组进行排序void sort(Line lines[], int n){//先按低端点的y坐标进行升序排序for (int i = 0; i < n; ++i){int min_index = i;for (int j = i + 1; j < n; ++j){if (lines[j].low_point.y < lines[min_index].low_point.y)min_index = j;}swap(lines[i], lines[min_index]);}//再将有序数组按低端点的x坐标升序排列，若x坐标相等，按inverse_k升序for (i = 0; i < n; ++i){int min_index = i;for (int j = i + 1; lines[j].low_point.y == lines[i].low_point.y; ++j){if (lines[j].low_point.x < lines[min_index].low_point.x)min_index = j;}swap(lines[i], lines[min_index]);if (i > 0 && lines[i].low_point.x == lines[i - 1].low_point.x){if (lines[i].is_active == 1 && lines[i - 1].is_active == 1){if (lines[i].inverse_k < lines[i - 1].inverse_k)swap(lines[i], lines[i - 1]);}}}}//创建一个边表EdgeTable* create_edge_table(Line lines[], int n){EdgeTable *edge_table = (EdgeTable*)malloc(sizeof(EdgeTable));edge_table->head = NULL;edge_table->next = NULL;sort(lines, n);Point lowest_point = get_lowest_point(lines, n);Point highest_point = get_highest_point(lines, n);EdgeTable *s = edge_table;for (int i = lowest_point.y; i <= highest_point.y; ++i){Bucket *bucket = (Bucket*)malloc(sizeof(Bucket));bucket->y = i;bucket->next = NULL;bucket->head = (EdgeNode*)malloc(sizeof(EdgeNode));bucket->head->next = NULL;EdgeNode *p = bucket->head;for (int j = 0; j < n; ++j){if (lines[j].is_active == 0)continue;if (lines[j].low_point.y == i){EdgeNode *q = (EdgeNode*)malloc(sizeof(EdgeNode));q->x = lines[j].low_point.x;q->y_max = lines[j].high_point.y;q->inverse_k = lines[j].inverse_k;q->next = NULL;p->next = q;p = q;}}s->next = bucket;s = bucket;}return edge_table;}//从边表中取出第一个不为空的桶初始化有效边表ActiveEdgeTable* init_active_table(EdgeTable *edge_table){ActiveEdgeTable *active_table = (ActiveEdgeTable*)malloc(sizeof(ActiveEdgeTable));active_table->y = edge_table->next->y;active_table->head = (EdgeNode*)malloc(sizeof(EdgeNode));active_table->head->next = NULL;EdgeNode *p = edge_table->next->head;EdgeNode *q = active_table->head;while (p->next != NULL){EdgeNode *s = (EdgeNode*)malloc(sizeof(EdgeNode));s->x = p->next->x;s->y_max = p->next->y_max;s->inverse_k = p->next->inverse_k;s->next = NULL;q->next = s;q = s;p = p->next;}return active_table;}//从有效边表中删除指定y_max的边结点void delete_edge(ActiveEdgeTable *active_table, int y_max){EdgeNode *p = active_table->head;while (p->next != NULL){EdgeNode *q = p->next;if (q->y_max == y_max){p->next = q->next;free(q);}elsep = p->next;}}//将一个边结点按次序添加到有效边表中void add_edge(ActiveEdgeTable *active_table, EdgeNode edge){EdgeNode *t = (EdgeNode*)malloc(sizeof(EdgeNode));t->x = edge.x;t->y_max = edge.y_max;t->inverse_k = edge.inverse_k;t->next = NULL;EdgeNode *p = active_table->head;while (p->next != NULL){EdgeNode *q = p->next;if ((edge.x < q->x) || (edge.x == q->x && edge.inverse_k < q->inverse_k)){p->next = t;t->next = q;return;}p = p->next;}p->next = t;}//更新有效边表，并与边表中对应的桶合并ActiveEdgeTable* update_active_table(ActiveEdgeTable *active_table, EdgeTable *edge_table) {//更新扫描线y++active_table->y;//删除y=ymax的边delete_edge(active_table, active_table->y);//更新边结点的数据EdgeNode *p = active_table->head->next;while (p != NULL){p->x += p->inverse_k;p = p->next;}//找到边表中对应的桶EdgeTable *q = edge_table;while ((q = q->next) != NULL && q->y != active_table->y);//如果找到，则进行合并if (q != NULL){EdgeNode *s = q->head;while ((s = s->next) != NULL){add_edge(active_table, *s);}}return active_table;}//画出多边形的边框void DrawPolygon(Point points[], int n){glBegin(GL_LINE_LOOP);for (int i = 0; i < n; ++i)glVertex2i(points[i].x, points[i].y);glEnd();}//画出x * y的网格void DrawGrid(int x, int y){glBegin(GL_LINES);//横线for (int i = 0; i <= y; ++i){glVertex2d(0, i);glVertex2d(x, i);}//竖线for (i = 0; i <= x; ++i){glVertex2d(i, 0);glVertex2d(i, y);}glEnd();}//用指定的像素大小填充多边形void Fill(Point points[], int n){Line *lines = create_lines(points, n);EdgeTable *edge_table = create_edge_table(lines, n);ActiveEdgeTable *active_table = init_active_table(edge_table);while (active_table->head->next != NULL){EdgeNode *p = active_table->head;int b = -1;while (p->next != NULL){if (b > 0){int left = p->x;int right = p->next->x;//如果不是局部最低点，则进行边界处理if (!(p->x - p->next->x >= -EPSILON && p->x - p->next->x <= EPSILON)){//处理左边界if (!(p->x - left >= -EPSILON && p->x - left <= EPSILON))left += 1;//处理右边界if (p->next->x - right >= -EPSILON && p->next->x - right <= EPSILON)right -= 1;}for (int i = left; i <= right; ++i){glBegin(GL_POINTS);glVertex2d(i, active_table->y);glEnd();glFlush();Sleep(50);}}p = p->next;b = -b;}active_table = update_active_table(active_table, edge_table);}}//初始化窗口，x和y指定窗口的坐标大小void Initial(){glClearColor(1.0f, 1.0f, 1.0f, 1.0f);glMatrixMode(GL_PROJECTION);gluOrtho2D(0.0, 20.0, 0.0, 15.0);}//窗口的显示回调函数void Display(){//使用当前背景色填充窗口glClear(GL_COLOR_BUFFER_BIT);//使用灰色画出网格线glColor3f(0.75f, 0.75f, 0.75f);DrawGrid(20, 14);glFlush();//多边形的顶点坐标Point points[] = { { 3, 1 },{ 6, 5 },{ 8, 1 },{ 12, 9 },{ 7, 8 },{ 3, 12 },{ 1, 7 } };//计算顶点个数int n = sizeof(points) / sizeof(Point);//使用黑色画出多边形的边框glColor3f(0.0f, 0.0f, 0.0f);DrawPolygon(points, n);glFlush();//指定点大小glPointSize(6.0f);//使用红色填充多边形glColor3f(1.0f, 0.0f, 1.0f);Fill(points, n);glFlush();}。