www.pudn.com > CG2Programs.rar > circleMidpoint.c

/* circleMidpoint, Chapter 3, p. 102 */

/* EXAMPLE STARTS HERE */
#include "device.h"

void circleMidpoint (int xCenter, int yCenter, int radius)
{
  int x = 0;
  int y = radius;
  int p = 1 - radius;
  void circlePlotPoints (int, int, int, int);

  /* Plot first set of points */
  circlePlotPoints (xCenter, yCenter, x, y);

  while (x < y) {
    x++;
    if (p < 0) 
      p += 2 * x + 1;
    else {
      y--;
      p += 2 * (x - y) + 1;
    }
    circlePlotPoints (xCenter, yCenter, x, y);
  }
}

void circlePlotPoints (int xCenter, int yCenter, int x, int y)
{
  setPixel (xCenter + x, yCenter + y);
  setPixel (xCenter - x, yCenter + y);
  setPixel (xCenter + x, yCenter - y);
  setPixel (xCenter - x, yCenter - y);
  setPixel (xCenter + y, yCenter + x);
  setPixel (xCenter - y, yCenter + x);
  setPixel (xCenter + y, yCenter - x);
  setPixel (xCenter - y, yCenter - x);
}
/* EXAMPLE ENDS HERE */

void main (int argc, char ** argv)
{
  long windowID = openGraphics (*argv, WINDOW_WIDTH, WINDOW_HEIGHT);
  setBackground (WHITE);
  setColor (BLACK);
  circleMidpoint (WINDOW_WIDTH/2, WINDOW_HEIGHT/2, WINDOW_WIDTH/4);
  sleep (10);
  closeGraphics (windowID);
}