#include <GL/gl.h>
#include <GL/glut.h>
#include <iostream>
#include <cmath>
#include <cstring>
#include <string>
using namespace std;
int x[]= {10,70,70,60,40,30,20};
int y[]= {10,10,50,40,60,20,30};
int vis[500][500]; //判断该坐标的点是否存在
void init()
{
  glClearColor (0.0, 0.0, 0.0, 0.0);
  glMatrixMode (GL_PROJECTION);
  gluOrtho2D (0.0, 200.0, 0.0, 150.0);
}
void MidBresenhamCircle()
{
  memset(vis,0,sizeof(vis));
  glClear(GL_COLOR_BUFFER_BIT);
  glLineWidth(2);
  glBegin(GL_LINES); //绘制多边形形状
  for(int i=0; i<7; ++i)
  {
    glVertex2i(x[i],y[i]);
    glVertex2i(x[(i+1)%7],y[(i+1)%7]);
  }
  glEnd();
  glFlush();
  glPointSize(2);
  glBegin(GL_POINTS);
  for(int i=x[1],j=y[1]; i<300; ++i) //特殊处理k=0的边
  {
    if(!vis[i][j])
    {
      glColor3f(0.0f,1.0f,0.0f);
      glVertex2i(i,j);
      vis[i][j]=1;
    }
    else
    {
      glColor3f(0.0f,0.0f,0.0f);
      glVertex2i(i,j);
      vis[i][j]=1;
    }
  }
  for(int j=y[1]; j<=y[2]; ++j) //特殊处理k不存在的边
  {
    for(int i=x[1]; i<300; ++i)
    {
      if(!vis[i][j])
      {
        glColor3f(0.0f,1.0f,0.0f);
        glVertex2i(i,j);
        vis[i][j]=1;
      }
      else
      {
        glColor3f(0.0f,0.0f,0.0f);
        glVertex2i(i,j);
        vis[i][j]=1;
      }
    }
  }
  for(int p=2; p<7; ++p)
  {
    int k=(y[(p+1)%7]-y[p])/(x[(p+1)%7]-x[p]); //求出斜率
    int x1=x[(p+1)%7],x0=x[p],y1=y[(p+1)%7],y0=y[p]; //根据斜率推导出这条直线的各个点
    if(y1<y0)
    {
      swap(x1,x0);
      swap(y1,y0);
    }
    for(int j=y0; j<=y1; ++j)
    {
      int i=(j-y0+k*x0)/k;
      for(int px=i; px<300; ++px)
      {
        if(!vis[px][j])
        {
          glColor3f(0.0f,1.0f,0.0f);
          glVertex2i(px,j);
          vis[px][j]=1;
        }
        else
        {
          glColor3f(0.0f,0.0f,0.0f);
          glVertex2i(px,j);
          vis[px][j]=0;
        }
      }
    }
  }
  glEnd();
  glFlush();
}
int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
  glutInitWindowPosition(100, 100);
  glutInitWindowSize(500, 500);
  glutCreateWindow("第一个opengl程序");
  init();
  glutDisplayFunc(MidBresenhamCircle);
  glutMainLoop();
  return 0;
}