upekux/nbis/libmindtct/line.c

/*******************************************************************************

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*******************************************************************************/


/***********************************************************************
      LIBRARY: LFS - NIST Latent Fingerprint System

      FILE:    LINE.C
      AUTHOR:  Michael D. Garris
      DATE:    03/16/1999

      Contains routines that compute contiguous linear trajectories
      between two coordinate points required by the NIST Latent
      Fingerprint System (LFS).

***********************************************************************
               ROUTINES:
                        line_points()
***********************************************************************/

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

#include "lfs.h"

/*************************************************************************
**************************************************************************
#cat: line_points - Returns the contiguous coordinates of a line connecting
#cat:               2 specified points.

   Input:
      x1      - x-coord of first point
      y1      - y-coord of first point
      x2      - x-coord of second point
      y2      - y-coord of second point
   Output:
      ox_list - x-coords along line trajectory
      oy_list - y-coords along line trajectory
      onum    - number of points along line trajectory
   Return Code:
      Zero      - successful completion
      Negative  - system error
**************************************************************************/
int line_points(int **ox_list, int **oy_list, int *onum,
                const int x1, const int y1, const int x2, const int y2)
{
   int asize;
   int dx, dy, adx, ady;
   int x_incr, y_incr;
   int i, inx, iny, intx, inty;
   double x_factor, y_factor;
   double rx, ry;
   int ix, iy;
   int *x_list, *y_list;

   /* Compute maximum number of points needed to hold line segment. */
   asize = max(abs(x2-x1)+2, abs(y2-y1)+2);

   /* Allocate x and y-pixel coordinate lists to length 'asize'. */
   x_list = (int *)malloc(asize*sizeof(int));
   if(x_list == (int *)NULL){
      fprintf(stderr, "ERROR : line_points : malloc : x_list\n");
      return(-410);
   }
   y_list = (int *)malloc(asize*sizeof(int));
   if(y_list == (int *)NULL){
      free(x_list);
      fprintf(stderr, "ERROR : line_points : malloc : y_list\n");
      return(-411);
   }

   /* Compute delta x and y. */
   dx = x2 - x1;
   dy = y2 - y1;

   /* Set x and y increments. */
   if(dx >= 0)
      x_incr = 1;
   else
      x_incr = -1;

   if(dy >= 0)
      y_incr = 1;
   else
      y_incr = -1;

   /* Compute |DX| and |DY|. */
   adx = abs(dx);
   ady = abs(dy);

   /* Set x-orientation. */
   if(adx > ady)
      inx = 1;
   else
      inx = 0;

   /* Set y-orientation. */
   if(ady > adx)
      iny = 1;
   else
      iny = 0;

   /*  CASE 1: |DX| > |DY|              */
   /*     Increment in X by +-1         */
   /*               in Y by +-|DY|/|DX| */
   /*        inx   =  1                 */
   /*        iny   =  0                 */
   /*        intx  =  1 (inx)           */
   /*        inty  =  0 (iny)           */
   /*  CASE 2: |DX| < |DY|              */
   /*     Increment in Y by +-1         */
   /*               in X by +-|DX|/|DY| */
   /*        inx   =  0                 */
   /*        iny   =  1                 */
   /*        intx  =  0 (inx)           */
   /*        inty  =  1 (iny)           */
   /*  CASE 3: |DX| == |DY|             */
   /*        inx   =  0                 */
   /*        iny   =  0                 */
   /*        intx  =  1                 */
   /*        inty  =  1                 */
   intx = 1 - iny;
   inty = 1 - inx;

   /*                                        DX           */
   /* x_factor = (inx * +-1) +  ( iny * ------------ )    */
   /*                                   max(1, |DY|)      */
   /*                                                     */
   x_factor = (inx * x_incr) + (iny * ((double)dx/max(1, ady)));

   /*                                        DY           */
   /* y_factor = (iny * +-1) +  ( inx * ------------ )    */
   /*                                   max(1, |DX|)      */
   /*                                                     */
   y_factor = (iny * y_incr) + (inx * ((double)dy/max(1, adx)));

   /* Initialize integer coordinates. */
   ix = x1;
   iy = y1;
   /* Set floating point coordinates. */
   rx = (double)x1;
   ry = (double)y1;

   /* Initialize to first point in line segment. */
   i = 0;

   /* Assign first point into coordinate list. */
   x_list[i] = x1;
   y_list[i++] = y1;

   while((ix != x2) || (iy != y2)){

      if(i >= asize){
         fprintf(stderr, "ERROR : line_points : coord list overflow\n");
         free(x_list);
         free(y_list);
         return(-412);
      }

      rx += x_factor;
      ry += y_factor;

      /* Need to truncate precision so that answers are consistent */
      /* on different computer architectures when truncating doubles. */
      rx = trunc_dbl_precision(rx, TRUNC_SCALE);
      ry = trunc_dbl_precision(ry, TRUNC_SCALE);

      /* Compute new x and y-pixel coords in floating point and  */
      /* then round to the nearest integer.                      */
      ix = (intx * (ix + x_incr)) + (iny * (int)(rx + 0.5));
      iy = (inty * (iy + y_incr)) + (inx * (int)(ry + 0.5));

      /* Assign first point into coordinate list. */
      x_list[i] = ix;
      y_list[i++] = iy;
   }

   /* Set output pointers. */
   *ox_list = x_list;
   *oy_list = y_list;
   *onum = i;

   /* Return normally. */
   return(0);
}