【OpenGL C++】画一个空心汉字和一个圆，并填充汉字（中点画线法，中点画圆法，种子填充法）

内容：画一个空心汉字和一个圆

设计一个画任意直线和圆的算法，可选所学的任一图形扫描转换算法（中点或bresenham算法），不能使用任何画线／画圆的API；
使用画线算法实现空心汉字的绘制，汉字必须为4划以上；
使用你设计的画圆算法绘制这个空心字的外接圆；
设计一种填充算法实现汉字的填充；

1.中点画圆法

生成八分之一圆，其他部分可以通过一系列的简单反射变换得到。
（1）已知圆心在原点的圆上的一点的(x,y)，函数circlePlotPoint()
根据对称性得到8个对称点，分别为(y,x),(y,-x),(x,-y),(-x,-y),(-y,-x),(-y,x),(-x,y)；
（2）函数circleMidpoint（）
如果此时点的位置为(X1,Y1),那么下一个点位置只可能是(X1+1,Y1)或者(X1+1,Y1-1)，根据判别式d:
d<0,应取(X1+1,Y1)为下一个点,d=d+2*x+3;
d>=0应取(X1+1,Y1-1)为下一个点,d=d+(x-y)+5;

2.中点画线法

（1）强制起点在终点左侧，如果不是的话，则交换两点；
（2）函数MidPoint()
分为四种情况，斜率0=<k<=1、斜率1<k、斜率-1 =<k<0和斜率k<-1时,根据每种情况下的判别式d,判断下一个点的位置；
（3） 函数setPoint（）
每画一个点，就将其对应的flag置为1，说明此点已填充，则边界上所有的点的flag都已经置为1，为填充时判断边界做了准备。

3.种子填充法

函数Flood（）
（1）先将种子像素压入栈；
（2）如果栈不为空，栈顶像素出栈；
（3）按左上右下的顺序搜索与出栈像素相邻的4个像素，若像素的flag值是1，说明该像素已填充，结束本次循环；若像素的flag值是0，说明该像素未填充，将该像素入栈。

#include <gl/glut.h>
#include <math.h>
#include <windows.h>
#include <iostream>
#include <vector>
#include <stack>
#include <stdlib.h>using namespace std;
int xc, yc, r;
int flag[2000][2000] = { 0 };
int winwidth = 500, winheight = 500;//窗口长宽//声明一个类
class screenPt
{public:screenPt(){x = y = 0;}void setCoords(GLint xCoordValue, GLint yCoordValue) {x = xCoordValue;y = yCoordValue;}GLint x, y;
};void init() {glClearColor(0, 0, 0, 0);//设置绘制窗口颜色为黑色glClear(GL_COLOR_BUFFER_BIT);//清除窗口显示内容/*设置为投影类型模式和其他观察参数*/glPointSize(1.0f);glColor3f(1.0, 0.0, 0.0);//设置颜色为红glMatrixMode(GL_PROJECTION);glLoadIdentity();//左上角坐标为（0，0），长宽为500gluOrtho2D(0, winwidth, winheight, 0);
}//画点
void setPixel(GLint xCoord, GLint yCoord) {glBegin(GL_POINTS);glVertex2i(xCoord, yCoord);glEnd();
}//八个对称点
void circlePlotPoints(GLint xc, GLint yc, screenPt circpt) {setPixel(xc + circpt.x, yc + circpt.y);setPixel(xc - circpt.x, yc + circpt.y);setPixel(xc + circpt.x, yc - circpt.y);setPixel(xc - circpt.x, yc - circpt.y);setPixel(xc + circpt.y, yc + circpt.x);setPixel(xc - circpt.y, yc + circpt.x);setPixel(xc + circpt.y, yc - circpt.x);setPixel(xc - circpt.y, yc - circpt.x);
}/*中心画圆法*/
void circleMidpoint(GLint xc, GLint yc, GLint radius) {glClear(GL_COLOR_BUFFER_BIT);//清除窗口显示内容screenPt circpt;//创建一个对象GLint p = 1 - radius;circpt.setCoords(0, radius);//显示圆弧上的八个点circlePlotPoints(xc, yc, circpt);while (circpt.x < circpt.y) {circpt.x++;if (p < 0) {p += 2 * circpt.x + 3;}else {circpt.y--;p += 2 * (circpt.x - circpt.y) + 5;}//显示圆弧上的八个点circlePlotPoints(xc, yc, circpt);}}class Point {public:Point();Point(GLint  _x, GLint _y) {x = _x;y = _y;}GLint x, y;
};// 种子填充
void Flood(int a, int b)   {//      (x - 1, y);  //left//       (x, y - 1);  //up//     (x + 1, y);  //right//     (x, y + 1);  //downint dx[4] = { -1, 0, 1,0 };int dy[4] = { 0, -1, 0,1 };stack<Point> q;q.push(Point(a, b));while (q.size()) {auto t = q.top();q.pop();for (int i = 0; i < 4; i++) {int n = t.x + dx[i];int m = t.y + dy[i];//cout << m << "  " << n << endl;if (flag[n][m])continue;flag[n][m] = 1;glBegin(GL_POINTS);glColor3f(255, 255, 0);glVertex2f(n ,m );glEnd();q.push(Point(n, m));glFlush();}}
}//画线之间的点
void setPoint(GLint x,GLint y) {glBegin(GL_POINTS);glColor3f(249, 216, 118);//glVertex2f(x, y);//指定顶点的值flag[(int)(x )][(int)(y )] = 1;glEnd();
}void MidPoint() {//将点的信息放到line中保存vector<Point> line;//第一部分连接点 4line.push_back(Point(240, 150));line.push_back(Point(255, 150));line.push_back(Point(255, 150));line.push_back(Point(265, 165));line.push_back(Point(250, 165));line.push_back(Point(265, 165));line.push_back(Point(240, 150));line.push_back(Point(250, 165));第2部分连接点 22line.push_back(Point(200, 185));line.push_back(Point(215, 185));line.push_back(Point(200, 185));line.push_back(Point(200, 220));line.push_back(Point(200, 220));line.push_back(Point(215, 220));line.push_back(Point(215, 210));line.push_back(Point(215, 220));line.push_back(Point(215, 185));line.push_back(Point(215, 190));line.push_back(Point(215, 190));line.push_back(Point(305, 190));line.push_back(Point(305, 185));line.push_back(Point(305, 190));line.push_back(Point(305, 185));line.push_back(Point(325, 185));line.push_back(Point(325, 185));line.push_back(Point(325, 220));line.push_back(Point(310, 220));line.push_back(Point(325, 220));line.push_back(Point(310, 210));line.push_back(Point(310, 220));line.push_back(Point(215, 210));line.push_back(Point(310, 210));第3部分连接点  36line.push_back(Point(180,240));line.push_back(Point(240, 240));line.push_back(Point(180, 240));line.push_back(Point(180, 250));line.push_back(Point(240, 240));line.push_back(Point(250, 225));line.push_back(Point(250, 225));line.push_back(Point(270, 225));line.push_back(Point(260, 240));line.push_back(Point(270, 225));line.push_back(Point(260, 240));line.push_back(Point(345, 240));line.push_back(Point(180, 250));line.push_back(Point(235, 250));line.push_back(Point(250, 250));line.push_back(Point(290, 250));line.push_back(Point(210, 290));line.push_back(Point(235,250));line.push_back(Point(210, 290));line.push_back(Point(230, 300));line.push_back(Point(190, 340));line.push_back(Point(230, 300));line.push_back(Point(190, 340));line.push_back(Point(195, 350));line.push_back(Point(195, 350));line.push_back(Point(245, 310));line.push_back(Point(245, 310));line.push_back(Point(320, 340));line.push_back(Point(320, 340));line.push_back(Point(325, 330));line.push_back(Point(265, 300));line.push_back(Point(325, 330));line.push_back(Point(265, 300));line.push_back(Point(310, 250));line.push_back(Point(310, 250));line.push_back(Point(345, 250));line.push_back(Point(345, 240));line.push_back(Point(345, 250));第四部分连接点 4line.push_back(Point(235, 285));line.push_back(Point(250, 250));line.push_back(Point(235, 285));line.push_back(Point(250, 290));line.push_back(Point(250, 290));line.push_back(Point(290, 250));//中点画线法for (int i = 0; i < line.size() - 1; i += 2) {double x0, y0, x1, y1;x0 = line[i].x;y0 = line[i].y;x1 = line[i + 1].x;y1 = line[i + 1].y;double A = y0 - y1;double B = x1 - x0;double k = -1 * (A / B);double t;double d;//强制起点在终点左侧，如果不是的话，则交换两点；if (x1 < x0) {t = x1;x1 = x0;x0 = t;t = y1;y1 = y0;y0 = t;}//斜率0=<k<=1if (k >= 0 && k <= 1) {d = (2 * A + B);while (x0 != x1) {setPoint(x0, y0);if (d <= 0) {x0 += 1;y0 += 1;d += (2 * (A + B));}else {x0++;d += (2 * A);}//glFlush();}}//斜率大于1if (k > 1) {d = (A + 2 * B);while (y0 != y1) {setPoint(x0, y0);if (d < 0) {y0 += 1;d += (2 * B);}else {y0 += 1;x0 += 1;d += (2 * (A + B));}//glFlush();}}//斜率大于等于-1 小于0时if (k >= -1 && k < 0) {d = (2 * A - B);while (x0 != x1) {setPoint(x0, y0);if (d < 0) {x0 += 1;d += (2 * A);}else {x0 += 1;y0 -= 1;d += (2 * (A - B));}//glFlush();}}//斜率小于-1时if (k < -1) {d = (int)(A - 2 * B);while (y0 != y1) {setPoint(x0, y0);if (d < 0) {y0 -= 1;x0 += 1;d += (2 * (A - B));}else {y0 -= 1;d -= (2 * B);}//glFlush();}}}//调用种子填充setPixel(210, 200);Flood(210,200);setPixel(245, 155);Flood(245, 155);setPixel(181, 241);Flood(181, 241);
}void display() {circleMidpoint(250, 250, 120);MidPoint();//glFlush();
}int main(int argc, char** argv) {glutInit(&argc, argv);//初始化glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);//设置绘制模式glutInitWindowPosition(400, 150); //设置窗口的位置glutInitWindowSize(winwidth, winheight);glutCreateWindow("绘制并填充”安“"); //创建窗口并赋予titleinit();glutDisplayFunc(display);glutMainLoop();}

结果：