line.c

Algorithms for Image Processing and Computer Vision Source Code

/* This is file LINE.C */
/*
** Copyright (C) 1993 DJ Delorie, 24 Kirsten Ave, Rochester NH 03867-2954
**
** This file is distributed under the terms listed in the document
** "copying.dj", available from DJ Delorie at the address above.
** A copy of "copying.dj" should accompany this file; if not, a copy
** should be available from where this file was obtained.  This file
** may not be distributed without a verbatim copy of "copying.dj".
**
** This file is distributed WITHOUT ANY WARRANTY; without even the implied
** warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*/

GrLine(x1, y1, x2, y2, c)
{
  int dx, dy, sx, sy;
  int count;
  int brc, brmax;

  sx = sy = 1;
  dx = x2 - x1;
  dy = y2 - y1;
  if (dx < 0)
  {
    dx *= -1;
    sx *= -1;
  }
  if (dy < 0)
  {
    dy *= -1;
    sy *= -1;
  }
  if (dx > dy)
  {
    brmax = dx;
    brc = dx / 2;
    GrPlot(x1, y1, c);
    for (count = dx; count; count--)
    {
      x1 += sx;
      brc += dy;
      if (brc > brmax)
      {
        brc -= dx;
        y1 += sy;
      }
      GrPlot(x1, y1, c);
    }
  }
  else
  {
    brmax = dy;
    brc = dy / 2;
    GrPlot(x1, y1, c);
    for (count = dy; count; count--)
    {
      y1 += sy;
      brc += dx;
      if (brc > brmax)
      {
        brc -= dy;
        x1 += sx;
      }
      GrPlot(x1, y1, c);
    }
  }
}