iseffil.m

改进等高线拟合代码

function [x, y, color]=iseffil(startpoint,direction,pathlength,plotting)

%	[x y] = iseffil(startpoint,direction,pathlength)		[f]
%	gives coordinates of the edge cntourpoint 		
%	by scanning a line which start at startpoint in the given direction
%	with pathlength. Possible directions are:
%	dir=0 -> horizontal
%	dir=2 -> vertical
%	dir=1 -> under +45 degrees (in the first quadrant)
%  dir=3 -> under -45 degrees (in the second quadrant)
%
%	color = 0  -> no edge
%	color = 1  -> 'white' line
%	color =-1  -> 'blach' line
%
%	A given line is processed in ascending x-values if possible.
%  So if x doesn't change it processed in ascending y-values.
%  The global matrix BEELD contains the pixelgrayvalues.
%
%  Plotting indicates whether the scanning lines are plotted.
%
% 21 april 1999
% Walter Verdonck,

% All the software included in this package is presented as is.
% It may be distributed freely. The author can, however, not be
% held responsible for any problems whatever.
% 
% Designed by Johan Baeten, Walter Verdonck
% Last updated: 29-03-2000
% [e-mail]

global B
global FITHANDLES
global UICTRHANDLES
global XSIZE
global YSIZE
global MAINFIG
global FILECHANGED
global BEELD

B=0.5;

xstart=startpoint(1);
ystart=startpoint(2);

if direction==0  
	yend=ystart; 
	if (xstart+pathlength-1)>=XSIZE 
		xend=XSIZE;
	else 	xend=xstart+pathlength-1;
	end
	data=BEELD(ystart,xstart:xend);
elseif direction==2 
	xend=xstart; 
	if (ystart+pathlength-1)>=YSIZE 
		yend=YSIZE;
	else 	yend=ystart+pathlength-1;
	end
	data=(BEELD(ystart:yend,xstart))';				
elseif direction==1 
	xend=xstart+pathlength-1;
	yend=ystart+pathlength-1;
	if xend>XSIZE
		yend=yend-(xend-XSIZE);
		xend=XSIZE;
	end
	if yend>YSIZE
		xend=xend-(yend-YSIZE);
		yend=YSIZE;
	end
	for i=0:(xend-xstart)
		data(i+1)=BEELD(ystart+i,xstart+i);
	end
elseif direction==3 
	xend=xstart+pathlength-1;
	yend=ystart-pathlength+1;
	if xend>XSIZE
		yend=yend+(xend-XSIZE);
		xend=XSIZE;
	end
	if yend<1
		xend=xend+(yend-1);
		yend=1;
	end
	for i=0:(xend-xstart)
		data(i+1)=BEELD(ystart-i,xstart+i);
	end
end


if plotting
   line([xstart,xend],[ystart,yend]);
end

j=length(data);

if min(data) > 170 
	color = 1;
elseif max(data) < 100
	color = (-1);
else color = 0;
end

if ~color 
	% de eigenlijke iseffilter met zijn recursieve betrekking
	yld(1)=data(1);
	yrd(j)=data(j);

	for i=2:j
		yld(i)=(1-B)*data(i)+B*yld(i-1);
	end
	for i=1:(j-1)
		yrd(j-i)=(1-B)*data(j-i)+B*yrd(j-i+1);
	end
	for i=3:(j-3)
		d1(i)=yrd(i+1)-yld(i-1);
		d2(i)=yrd(i+1)+yld(i-1)-2*data(i);		
	end
	[yt i]=max(abs(d1(1:j-3)));

	if i < (j-3)
		if d2(i-1)*d2(i)<0
			xr=i-1-abs(d2(i))/(abs(d2(i-1))+abs(d2(i)));
		else	xr=i-1+abs(d2(i))/(abs(d2(i+1))+abs(d2(i)));
		end
	else xr=i-1;
	end
		
	if direction==0  
		x=xstart+xr;
		y=ystart;
	elseif direction==2 
		y=ystart+xr;
		x=xstart;
	elseif direction==1 
		x=xstart+xr;
		y=ystart+xr;
	elseif direction==3 
		x=xstart+xr;
		y=ystart-xr;
	end
	
	else x=0;y=0;
end