142.抛物样条曲线

/* draw Parspl */
#include <graphics.h>
#include <math.h>
#include <stdio.h>
void parspl(p,n,k,e)
int p[][2],n,k,e;
{
  int x,y,i,j,m;
  float t1,t2,t3,t,a,b,c,d;
  if(e==1)
  {
    m=n;
    p[0][0]=p[1][0];
    p[0][1]=p[1][1];
    p[n+1][0]=p[n][0];
    p[n+1][1]=p[n][1];
  }
  else
  {
    m=n+1;
    p[0][0]=p[n][0];
    p[0][1]=p[n][1];
    p[m][0]=p[1][0];
    p[m][1]=p[1][1];
    p[m+1][0]=p[2][0];
    p[m+1][1]=p[2][1];
  }
  t=0.5/k;
  moveto(p[1][0],p[1][1]);
  for(i=0;i<m-1;i++)
  {
    for(j=1;j<k;j++)
    {
      t1=j*t;
      t2=t1*t1;
      t3=t2*t1;
      a=4.0*t2-t1-4.0*t3;
      b=1.0-10.0*t2+12.0*t3;
      c=t1+8.0*t2-12.0*t3;
      d=4.0*t3-2.0*t2;
      x=a*p[i][0]+b*p[i+1][0]+c*p[i+2][0]+d*p[i+3][0];
      y=a*p[i][1]+b*p[i+1][1]+c*p[i+2][1]+d*p[i+3][1];
      lineto(x,y);
    }
    lineto(p[i+2][0],p[i+2][1]);
  }
}
void marking(a,n)
int a[][2],n;
{
  int i;
  setfillstyle(1,WHITE);
  for(i=1;i<=n;i++)
  {
    circle(a[i][0],a[i][1],2);
    floodfill(a[i][0],a[i][1],RED);
  }
}
void main()
{
  int i,n,c,p[50][2],px,py;
  char fname[10],ch;
  FILE *fp;
  int gdriver=DETECT,gmode;
  clrscr();
  printf("Please input point numer: ");
  scanf("%d",&n);
  printf("Please input name of the file with the point data:\n >> ");
  scanf("%s",fname);
  if((fp=fopen(fname,"r"))==NULL)
  {
    printf("File %s does not exist! Do you want to create it? Y/N ",fname);
    ch=getch();
    if(ch=='Y'||ch=='y')
    {
      if((fp=fopen(fname,"w+"))==NULL)
      {
        printf("\nError! Can't create file %s!",fname);
        exit(1);
      }
      printf("\nPlease input %d pair coordinates (x,y) of the points:\n",n);
      for(i=0;i<n;i++)
      {
        scanf("%d%d",&px,&py);
        fprintf(fp,"%d %d ",px,py);
      }
            rewind(fp);
    }
    else
      exit(1);
  }
  rewind(fp);
  for(i=1;i<=n;i++)
    fscanf(fp,"%d%d",&p[i][0],&p[i][1]);
  fclose(fp);
  printf("Please input the figure type: FREE--1, Close--2: ");
  scanf("%d",&c);
  initgraph(&gdriver,&gmode,"c:\\tc");
  cleardevice();
  setbkcolor(9);
  setcolor(4);
  marking(p,n);
  outtextxy(80,460,"Press any key to continue...");
  getch();
  parspl(p,n,10,c);
  outtextxy(80,460,"Press any key to quit...    ");
  getch();
  closegraph();
}