From:	"Alexei A. Frounze" <see_below AT the_message_body DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: help a semi-newbie with some graphics....
Date:	Sat, 27 May 2000 23:19:50 +0400
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Standard Bresenham's line drawing function looks like this:

-------------------------8<-------------------------------
void line (int x1, int y1, int x2, int y2, char color) {
  int sx, sy, dx1, dy1, dx2, dy2, x, y, m, n, k=0, cnt;

  sx = x2-x1;
  sy = y2-y1;

  if (sx > 0) dx1 = 1;
  else if (sx < 0) dx1 = -1;
  else dy1 = 0;

  if (sy > 0) dy1 = 1;
  else if (sy < 0) dy1 = -1;
  else dy1 = 0;

  m = abs (sx);
  n = abs (sy);

  dx2 = dx1;
  dy2 = 0;

  if (m < n) {
    m = abs (sy);
    n = abs (sx);
    dx2 = 0;
    dy2 = dy1;
  };

  x = x1; y = y1;
  cnt = m+1;
  while (cnt--) {
    putpixel (x, y, color);
    k += n;
    if (k < m) {
      x += dx2;
      y += dy2;
    }
    else {
      k -= m;
      x += dx1;
      y += dy1;
    };
  };
}
-------------------------8<-------------------------------

Good Luck
Alexei A. Frounze
-----------------------------------------
E-mail:   alexfru [AT] chat [DOT] ru
Homepage: http://alexfru.chat.ru
Mirror:   http://members.xoom.com/alexfru

"DeepBlack (Murray Evans)" wrote:
> 
> Right, I've got a working pixel routine, a working rectangle drawing
> routine, and working vertical and horizontal line routines, which can all
> write to either the screen or a 'virtual' screen set up in memory. My
> problem arrises with my line drawing routine to cope with lines that are not
> horizontal/vertical.

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