Edge filling algorithm implemented by OpenGL

Time:2021-11-25

The idea of edge filling: enumerate each edge, and perform the filling operation on the pixels on the right of this edge, that is, remove it if there is filling, and fill it if there is no filling

#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]; // Judge whether the coordinate point exists
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); // Draw polygon shape
 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) // special treatment for edges with k = 0
 {
  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) // special treatment for edges where K does not exist
 {
  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]); // Find the slope
  int x1=x[(p+1)%7],x0=x[p],y1=y[(p+1)%7],y0=y[p]; // The points of the line are derived from the slope
  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 ("the first OpenGL program");
 init();
 glutDisplayFunc(MidBresenhamCircle);
 glutMainLoop();
 return 0;
}

effect

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