intline.m

function [x, y] = intline(x1, x2, y1, y2)
%INTLINE Integer-coordinate line drawing algorithm.
%  [X, Y] = INTLINE(X1, X2, Y1, Y2) computes an
%  approximation to the line segment joining (X1, Y1) and
%  (X2, Y2) with integer coordinates.  X1, X2, Y1, and Y2
%  should be integers.  INTLINE is reversible; that is,
%  INTLINE(X1, X2, Y1, Y2) produces the same results as
%  FLIPUD(INTLINE(X2, X1, Y2, Y1)).

%   Copyright 1993-2002 The MathWorks, Inc.  Used with permission.
%   $Revision: 1.4 $  $Date: 2003/11/21 14:38:20 $

dx = abs(x2 - x1);
dy = abs(y2 - y1);

% Check for degenerate case.
if ((dx == 0) & (dy == 0))
   x = x1;
   y = y1;
  return;
end

flip = 0;
if (dx >= dy)
   if (x1 > x2)
      % Always "draw" from left to right.
      t = x1; x1 = x2; x2 = t;
      t = y1; y1 = y2; y2 = t;
      flip = 1;
   end
   m = (y2 - y1)/(x2 - x1);
   x = (x1:x2).';
   y = round(y1 + m*(x - x1));
else
   if (y1 > y2)
      % Always "draw" from bottom to top.
      t = x1; x1 = x2; x2 = t;
      t = y1; y1 = y2; y2 = t;
      flip = 1;
   end
   m = (x2 - x1)/(y2 - y1);
   y = (y1:y2).';
   x = round(x1 + m*(y - y1));
end

if (flip)
   x = flipud(x);
   y = flipud(y);
end