How to draw a circle in c++?

Question

linux

Hello. Need to draw a circle in a simple ubuntu console project. I am using gcc. I googled, to solve such a problem, windows.h or graphics.h are used everywhere, but gcc swears at this. Please tell me how it is possible to solve this problem.

Answer 1

Here is an easy way:

#include <GL/glut.h>
#include <math.h>
// compile:
// gcc -Wall -Wextra -Werror -lglut -lGL -lm -std=gnu99 -D_GNU_SOURCE opengl.c -o openglcircle

#define _U_    __attribute__((__unused__))
// exit by ctrl+q or escape
void keyPressed(unsigned char key, _U_ int x, _U_ int y){
  int mod = glutGetModifiers(); // window = glutGetWindow()
  if(mod == GLUT_ACTIVE_CTRL && key == 'q') exit(0);
  else if(key == 27) exit(0);
}

void DrawCircle(float cx, float cy, float r, int num_segments){
  float theta = 2. * M_PI / (float)num_segments;
  float c, s, t, x = r, y = 0.;
  sincosf(theta, &s, &c);
  glBegin(GL_LINE_LOOP);
  for(int ii = 0; ii < num_segments; ii++){
    glVertex2f(x + cx, y + cy);
    t = x;
    x = c * x - s * y;
    y = s * t + c * y;
  }
  glEnd();
}

void display(){
  glClear(GL_COLOR_BUFFER_BIT);
  DrawCircle(0.,0.,0.5,100);
  glFlush();
}

int main(int argc, char** argv){
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(400, 400);
  glutCreateWindow("A Simple Circle");
  glutDisplayFunc(display);
  glutKeyboardFunc(keyPressed);
  glutMainLoop();
}

And, I'm sorry, I didn't notice about C++. Well, okay, anyway, I don’t know C ++ and don’t want to know!
PS And here is a clean console:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char *drawCircle(int R, int geom){
  if(R > 200 || R < 1) return NULL;
  int S, i, Y = 2 * R + 2;
  if(geom)
    S = Y * (R + 1);
  else
    S = Y * (Y - 1);
  char *buf = malloc(S+1);
  if(!buf) return NULL;
  memset(buf, ' ', S);
  buf[S] = 0;
  for(i = Y-1; i < S; i+=Y) buf[i] = '\n';
  inline void DrawPixel(int x, int y){
    if(geom){
      if(y%2==0) buf[Y * y/2 + x] = '*';
    }else{
      buf[Y * y + x] = '*';
    }
  }
  // Bresenham's circle algorithm
  int x = R;
  int y = 0;
  int radiusError = 1-x;
  while(x >= y){
    DrawPixel(x + R,   y + R);
    DrawPixel(y + R,   x + R);
    DrawPixel(-x + R,  y + R);
    DrawPixel(-y + R,  x + R);
    DrawPixel(-x + R, -y + R);
    DrawPixel(-y + R, -x + R);
    DrawPixel(x + R,  -y + R);
    DrawPixel(y + R,  -x + R);
    y++;
    if (radiusError < 0){
      radiusError += 2 * y + 1;
    }else{
      x--;
      radiusError += 2 * (y - x) + 1;
    }
  }
  return buf;
}

int main(int argc, char **argv){
  int i, R;
  char *buf;
  for(i = 1; i < argc; i++){
    if(!(buf = drawCircle(R = atoi(argv[i]), 1))){
      printf("Wrong parameter %s\n", argv[i]);
      continue;
    }
    printf("\nCircle with R = %d:\n%s\n", R, buf);
    free(buf); buf = NULL;
  }
  return 0;
}

Bresenham's algorithm, the second argument of the drawCircle function sets a correction for the geometry of the terminal: if you suddenly have a letter height equal to the width in the terminal, then write 0, if the height is 2 times greater than the width, write 1.

Answer 2

In the console? And in niks does the console support graphics at all?

Answer 3

For the lab at the university, I had to use Code::Blocks under Wine + graphics.h

Answer 4

Terrible.
Where is this from and why?

Answer 5

In console pseudographics, if only, draw with pens.

Answer 6

The algorithm for drawing a circle is something like this:

//Цикл от 0 до 360 градусов
for (int i = 0; i < 360; i++) {

  //Перевод из градусов в радианы
  double a = i * M_PI / 180;
  
  //Задаём нужный радиус
  double r = 1; 
  
  //Вычисляем координаты
  double x = r * cos(a);
  double y = r * sin(a);
}