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% Johan.baeten@mech.kuleuven.ac.beglobal Bglobal FITHANDLESglobal UICTRHANDLESglobal XSIZEglobal YSIZEglobal MAINFIGglobal FILECHANGEDglobal BEELDB=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);	endelseif 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);	endendif plotting   line([xstart,xend],[ystart,yend]);endj=length(data);if min(data) > 170 	color = 1;elseif max(data) < 100	color = (-1);else color = 0;endif ~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