Image:Chebyshev.png

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//

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#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>

#define PI 3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825
#define PI2 (PI*2)
#define SQ2 1.414213562373095048801688724209698078569671875376948073176679737990732478462
#define FI 1.618033988749894848204586834365638117720309179805762862135448622705260462818902449707207204

#define SX 201
#define SY 201

#define BPL ((SX*3+3)&~3)

unsigned char bhdr[54]={
0x42, 0x4D, 0x36, 0x00, 0x30, 0x00, 0x00, 0x00, 0x00, 0x00, 0x36, 0x00, 0x00, 0x00, 0x28, 0x00,
0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x01, 0x00, 0x18, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x30, 0x00, 0x12, 0x0B, 0x00, 0x00, 0x12, 0x0B, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

unsigned char po[BPL];

double gr[SY][SX][3];

void drawit();

int main(int a, char **b) {
  FILE *o;
  int x, y, c; //Some variable declarations may not be relevant
  double t;
  char *p;

  srand(time(0));
  drawit();
  
  p=bhdr+2; *p++=x=54+BPL*SY; *p++=x>>=8; *p++=x>>=8; *p=x>>=8;
  p=bhdr+18; *p++=x=SX; *p++=x>>=8; *p++=x>>=8; *p++=x>>=8;
  *p++=x=SY; *p++=x>>=8; *p++=x>>=8; *p=x>>=8;

  if(!(o=fopen("func.bmp", "wb"))) {
    fclose(o);
    printf("Couldn't open output file.\n");
    return(0);
  }
  
  fwrite(bhdr, 54, 1, o);

  for(x=SX*3;x<BPL;++x) po[x]=0;
  
  for(y=SY-1;~y;--y) {
    for(x=0,p=po;x<SX;++x) for(c=2;~c;--c) *p++=(t=gr[y][x][c])<=0?0:(t>=1?255:t*255);
    fwrite(po, BPL, 1, o);
  }

  fclose(o);
  return(0);
}

double minx, miny, maxx, maxy, dlx, dly;

double cr, cg, cb;

void func(int f, double x, double *y, double *dydx) {
  double x2, x3, x4, x5, x6, x7;
  x2=x*x;
  x3=x2*x;
  x4=x3*x;
  x5=x4*x;
  x6=x5*x;
  x7=x6*x;
  switch(f) {
    //x
    case 0: *y=x; *dydx=1; break;
    //sinh(x)
    case 1: *y=(exp(x)-exp(-x))/2; *dydx=(exp(x)+exp(-x))/2; break;
    //cosh(x)
    case 2: *y=(exp(x)+exp(-x))/2; *dydx=(exp(x)-exp(-x))/2; break;
    //tanh(x)
    case 3: *y=(exp(x)-exp(-x))/(exp(x)+exp(-x)); *dydx=1-*y**y; break;
    //Chebyshev 0-7
    case 100: *y=1; *dydx=0; break;
    case 101: *y=x; *dydx=1; break;
    case 102: *y=2*x2-1; *dydx=4*x; break;
    case 103: *y=4*x3-3*x; *dydx=12*x2-3; break;
    case 104: *y=8*x4-8*x2+1; *dydx=32*x3-16*x; break;
    case 105: *y=16*x5-20*x3+5*x; *dydx=80*x4-60*x2+5; break;
    case 106: *y=32*x6-48*x4+18*x2-1; *dydx=192*x5-192*x3+38*x; break;
    case 107: *y=64*x7-112*x5+56*x3-7*x; *dydx=448*x6-560*x4+168*x2-7; break;
    default: *y=100; *dydx=0; break;
  }
}

void subp(int x, int y, double r, double g, double b) {
  if(x>=0&&y>=0&&x<SX&&y<SY) {
    gr[y][x][0]-=r; gr[y][x][1]-=g; gr[y][x][2]-=b;
  }
}

void drawdot(double x, double y) {
  int ix, iy;
  double dx, dy, ax, ay;
  x=(x-minx)/(maxx-minx)*(SX-1)+.5;
  y=(y-maxy)/(miny-maxy)*(SY-1)+.5;
  ix=floor(x); dx=x-ix; iy=floor(y); dy=y-iy;
  ax=1-dx; ay=1-dy;
  subp(ix-1, iy-1, cr*ax*ay*.05, cg*ax*ay*.05, cb*ax*ay*.05);
  subp(ix  , iy-1, cr   *ay*.05, cg   *ay*.05, cb   *ay*.05);
  subp(ix+1, iy-1, cr*dx*ay*.05, cg*dx*ay*.05, cb*dx*ay*.05);
  subp(ix-1, iy  , cr*ax   *.05, cg*ax   *.05, cb*ax   *.05);
  subp(ix  , iy  , cr      *.05, cg      *.05, cb      *.05);
  subp(ix+1, iy  , cr*dx   *.05, cg*dx   *.05, cb*dx   *.05);
  subp(ix-1, iy+1, cr*ax*dy*.05, cg*ax*dy*.05, cb*ax*dy*.05);
  subp(ix  , iy+1, cr   *dy*.05, cg   *dy*.05, cb   *dy*.05);
  subp(ix+1, iy+1, cr*dx*dy*.05, cg*dx*dy*.05, cb*dx*dy*.05);
}

void drawhorz(double y) {
  int ix, iy;
  double dy, ay;
  y=(y-maxy)/(miny-maxy)*(SY-1)+.5;
  iy=floor(y); dy=y-iy;
  ay=1-dy;
  for(ix=0;ix<SX;++ix) {
    subp(ix  , iy-1, cr   *ay    , cg   *ay    , cb   *ay    );
    subp(ix  , iy  , cr          , cg          , cb          );
    subp(ix  , iy+1, cr   *dy    , cg   *dy    , cb   *dy    );
  }
}

void drawvert(double x) {
  int ix, iy;
  double dx, ax;
  x=(x-minx)/(maxx-minx)*(SX-1)+.5;
  ix=floor(x); dx=x-ix;
  ax=1-dx;
  for(iy=0;iy<SY;++iy) {
    subp(ix-1, iy  , cr*ax       , cg*ax       , cb*ax       );
    subp(ix  , iy  , cr          , cg          , cb          );
    subp(ix+1, iy  , cr*dx       , cg*dx       , cb*dx       );
  }
}

void drawaxes() {
  drawhorz(0);
  drawvert(0);
}

void drawgrid() {
  int a, b;
  for(a=ceil(miny/dly)-1;a<=floor(maxy/dly)+1;++a) drawhorz(a*dly);
  for(a=ceil(minx/dlx)-1;a<=floor(maxx/dlx)+1;++a) drawvert(a*dlx);
}

void drawfunc(int f) {
  double x, y, dydx, pfx, pfy;
  pfx=(maxx-minx)/(SX-1);
  pfy=(maxy-miny)/(SY-1);
  for(x=minx;x<maxx;x+=.1*pfx/sqrt(1+dydx*dydx/((pfy*pfy)/(pfx*pfx)))) {
    func(f, x, &y, &dydx);
    drawdot(x, y);
  }
}

void drawit() {
  int x, y, c;
  for(y=0;y<SY;++y) for(x=0;x<SY;++x) for(c=0;c<3;++c) gr[y][x][c]=1;

  //Chebyshev 0, 1, 2, 3, 4, 5, 6, 7
  minx=miny=-5/4.; maxx=maxy=5/4.; dlx=dly=1;
  cr=.6; cg=.6; cb=.6;
  drawfunc(100);
  cr=.1; cg=.8; cb=.8;
  drawfunc(101);
  cr=.8; cg=.8; cb=.1;
  drawfunc(102);
  cr=.8; cg=.1; cb=.8;
  drawfunc(103);
  cr=.1; cg=.1; cb=.8;
  drawfunc(104);
  cr=.1; cg=.1; cb=.1;
  drawfunc(105);
  cr=.1; cg=.8; cb=.1;
  //drawfunc(106);
  cr=.8; cg=.1; cb=.1;
  //drawfunc(107);

/* //sinh, cosh, tanh
  minx=miny=-5; maxx=maxy=5; dlx=dly=1;
  cr=.1; cg=cb=.8;
  drawfunc(1);
  cg=.1; cb=cr=.8;
  drawfunc(2);
  cb=.1; cr=cg=.8;
  drawfunc(3);
*/  
  cr=cg=cb=.8;
  drawaxes();
  cr=cg=cb=.1;
  drawgrid();
  cr=cg=cb=.025; dlx=dly=.1;
  drawgrid();
}
//

[edit] Historio de la dosiero

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• (del) (cur) 01:04, 12 September 2004 . . en:User:Cyp Cyp ( en:User_talk:Cyp Talk) . . 201x201 (26147 bytes) (Graph of Chebyshev polynomials)