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  1. #include<stdio.h>
  2. #include<math.h>
  3.  
  4. #define MAX_POINTS 10
  5.  
  6. FILE* set_plot(int n,double p[][2])
  7. {
  8.     FILE* gp=popen("gnuplot -persistent","w");
  9.     fprintf(gp,"set title 'bezier curve'\n");
  10.     fprintf(gp,"set xrange[0:150]\n");
  11.     fprintf(gp,"set yrange[0:150]\n");
  12.     fprintf(gp,"set grid\n");
  13.  
  14.     fprintf(gp, "plot '-' with linespoints dt 2 pointsize 1.5 linewidth 2 linecolor rgb 'red' title 'Control Points', "
  15.                     "'-' with linespoints pointtype 7 pointsize 1.5 linewidth 3 linecolor rgb 'blue' title 'Bezier Curve'\n");
  16.  
  17.     // Control points
  18.     for(int i = 0; i <= n; i++) {
  19.         fprintf(gp, "%f %f\n", p[i][0], p[i][1]);
  20.     }
  21.     fprintf(gp, "e\n");
  22.  
  23.     return gp;
  24. }
  25.  
  26. void plot_curve(FILE* gp,double result[2])
  27. {
  28.     fprintf(gp, "%f %f\n", result[0], result[1]);
  29. }
  30.  
  31. // De Casteljau Algorithm
  32. void de_casteljau(double points[][2],int n, double t,double result[2])
  33. {
  34.     double temp[MAX_POINTS][2];
  35.  
  36.     // Copy original points
  37.     for(int i = 0; i <= n; i++)
  38.     {
  39.         temp[i][0] = points[i][0];
  40.         temp[i][1] = points[i][1];
  41.     }
  42.  
  43.     // Iteratively interpolate
  44.     for(int k = 1; k <= n; k++)
  45.     {
  46.         for(int i = 0; i <= n - k; i++)
  47.         {
  48.             temp[i][0] = (1 - t) * temp[i][0] + t * temp[i+1][0];
  49.             temp[i][1] = (1 - t) * temp[i][1] + t * temp[i+1][1];
  50.         }
  51.     }
  52.  
  53.     // Final point
  54.     result[0] = temp[0][0];
  55.     result[1] = temp[0][1];
  56. }
  57.  
  58. int main()
  59. {
  60.     int n = 3; // cubic Bezier (4 control points)
  61.  
  62.     double points[MAX_POINTS][2] = {
  63.         {10, 10},
  64.         {30, 120},
  65.         {100, 120},
  66.         {140, 20}
  67.     };
  68.  
  69.     FILE* gp = set_plot(n, points);
  70.  
  71.     double result[2];
  72.  
  73.     // Generate curve points
  74.     for(double t = 0.0; t <= 1.0; t += 0.01)
  75.     {
  76.         de_casteljau(points, n, t, result);
  77.         plot_curve(gp, result);
  78.     }
  79.  
  80.     fprintf(gp, "e\n"); // end Bezier curve data
  81.     pclose(gp);
  82.  
  83.     return 0;
  84. }
Success #stdin #stdout #stderr 0s 5316KB
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Standard output is empty
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sh: 1: gnuplot: not found
https://ideone.com/jgNAPf
language:
C (gcc 8.3)
created:
3 hours ago
visibility:
public

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