src/shline2s.c

/*
 *  PROGRAM NAME:  sh
 *
 *  (c) COPYRIGHT INTERNATIONAL BUSINESS MACHINES
 *  CORPORATION 12/1/2001.  ALL RIGHTS RESERVED.
 *
 *  Please refer to the LICENSE file in the top directory
 *
 *      author: Mike Henderson mhender@watson.ibm.com
 */

static char *id="@(#) $Id: shline2s.c,v 1.2 2006/08/17 19:28:17 mhender Exp $";

#include <shInternal.h>
#include <math.h>

void shline2s(int *i0,int *j0,int *i1,int *j1,int *ixoff,int *iyoff)
 {
  float zz;
  float xc,yc;
  float dx,dy;
  int ipix,jpix;

/*   draw a line segment */

  if((*i0)==(*i1)&&(*j0)==(*j1))
   {
    if((*i0)>0&&(*i0)<shIMax&&(*j0)>0&&(*j0)<shJMax)
     {
      zz=0.;
      shsetp(i0,j0,&sh_rl,&sh_gl,&sh_bl,&zz);
     }
    return;
   }

  xc=(*i0);
  yc=(*j0);
  dx=(*i1)-xc;
  dy=(*j1)-yc;
  zz=0.;
  while(fabs(dx)>.5||fabs(dy)>.5)
   {
    ipix=xc+.5+(*ixoff);
    jpix=yc+.5+(*iyoff);
    if(ipix>0&&ipix<shIMax&&jpix>0&&jpix<shJMax)shsetp(&ipix,&jpix,&sh_rl,&sh_gl,&sh_bl,&zz);

    dx=(*i1)-xc;
    dy=(*j1)-yc;
    if(abs(dx)>.5||abs(dy)>.5)
     {
      if(abs(dx)>abs(dy))
       {
        if(dx>0)
         {
          xc=xc+1;
          yc=yc+dy/dx;
         }else{
          xc=xc-1;
          yc=yc-dy/dx;
         }
       }else{
        if(dy>0)
         {
          yc=yc+1;
          xc=xc+dx/dy;
         }else{
          yc=yc-1;
          xc=xc-dx/dy;
         }
       }
     }
    dx=(*i1)-xc;
    dy=(*j1)-yc;
   }

  return;
 }

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