cliplin1.m

很好用的统计模式识别工具箱

function [x1,y1,x2,y2,in]=cliplin1(alpha,theta,window)
% [x1,y1,x2,y2,in]=cliplin1(alpha,theta,window)
%
% CLIPLIN1 clips the line given by the equation alpha*x=theta along
%   the window. It returns two points on the border of the window.
%   If the line is in the window then the argument is equal to 1
%   else it returns 0.
%
% See also CLIPLIN2.
%
% Statistical Pattern Recognition Toolbox, Vojtech Franc, Vaclav Hlavac
% (c) Czech Technical University Prague, http://cmp.felk.cvut.cz
% Written Vojtech Franc (diploma thesis) 20.10.1999, 23.12.1999
% Modifications
% 24. 6.00 V. Hlavac, comments polished.

minx=window(1);
maxx=window(2);
miny=window(3);
maxy=window(4);

x=zeros(4,1);
y=zeros(4,1);

if alpha(1)==0,
   if alpha(2)~=0,
      x1=minx;
      y1=theta/alpha(2);
      x2=maxx;
      y2=y1;
      in=1;
   else
      % if alpha == 0 then it means the bad input.
      x1=0;
      y1=0;
      x2=0;
      y2=0;
      in=0;
   end
elseif alpha(2)==0,
   x1=theta/alpha(1);
   y1=miny;
   x2=x1;
   y2=maxy;
   in=1;
else
   y(1)=maxy;
   x(1)=(theta-alpha(2)*y(1))/alpha(1);
   y(2)=miny;
   x(2)=(theta-alpha(2)*y(2))/alpha(1);

   x(3)=maxx;
   y(3)=(theta-alpha(1)*x(3))/alpha(2);
   x(4)=minx;
   y(4)=(theta-alpha(1)*x(4))/alpha(2);

   j=0;
   for i=1:4,
      if x(i) <= maxx & x(i) >= minx & y(i) <= maxy & y(i) >= miny,
         if j==0,
            j=j+1;
            x1=x(i);
            y1=y(i);
         elseif j==1,
            j=j+1;
            x2=x(i);
            y2=y(i);
         end
      end
   end

   if j<2,
      x1=0;
      y1=0;
      x2=0;
      y2=0;
      in=0;
   else
      in=1;
   end
end % elseif alpha(2)==0