function isefcall()

global XSIZE
global YSIZE
global MAINFIG
global FITHANDLES
global BEELD

BEELD = get(MAINFIG, 'userdata');
%cirkel;
%set(MAINFIG, 'userdata', BEELD);

%SIZE = max(XSIZE,YSIZE);
SIZE=32;
routine('new'); %	clear lijst van punten 
maxnrofpoints = 12;
error = 0;
direction = 0;
%	scan een eerste horizontale lijn om te kunnen starten
[x y] = iseffil([1,YSIZE], 0, XSIZE,1);
addpoint(x,y);
yp = floor(YSIZE/8);
%	scan een tweede horizontale lijn om verder te kunnen 
[x y] = iseffil([1,YSIZE-yp], 0, XSIZE,1);
addpoint(x,y);

if ((get(FITHANDLES(1,12), 'value'))<2) 
	seterror('Something went wrong, i am very sorry.');
	error = 1;
end
nrofpoints = get(FITHANDLES(1,12), 'value');
rotate = 0; 	
while (error==0)
	%nrofpoints = get(FITHANDLES(1,12), 'value');	
	x2 = get(FITHANDLES(3,nrofpoints),'value');
        y2 = get(FITHANDLES(4,nrofpoints),'value');
	x1 = get(FITHANDLES(3,nrofpoints-1),'value');
        y1 = get(FITHANDLES(4,nrofpoints-1),'value');
        tangens=(x1-x2)/(y1-y2);
	xstart=round(x2);
        ystart=round(y2);
        	if (abs(tangens) < 0.5)
        		direction = 0;
        		
	        elseif (tangens > 0.5) & (tangens < 2)
	        	direction = 3;
	        	
		elseif (abs(tangens) > 2)
			direction = 2;
	        	
        	elseif (tangens < -0.5) & (tangens > -2)
	        	direction = 1;
	        	
		end
		
		direction=mod(direction+rotate,4);
		
		if direction==0  
              	        	        	ystart=ystart-yp;
			if inbox(xstart,ystart)
                                xstart=xstart-(SIZE/2);				if xstart < 1 		        		xstart = 1;		        	end
			else error = 1;
			end
                elseif direction==2 
			xstart=xstart-(sign(x1-x2)*yp);
			if inbox(xstart,ystart)
          	                ystart=ystart-(SIZE/2);
	        		if ystart < 1
	        			ystart = 1;
		        	end
	        	else error = 1;
			end
                elseif direction==1 
             	        xstart = xstart+yp;
	        	ystart = ystart-yp;
			if inbox(xstart,ystart)
             	                xstart = xstart-SIZE/2;
	        	        ystart = ystart-SIZE/2;
	        		if ystart<1
					xstart=xstart-(ystart-1);
					ystart=1;
				end
		        	if xstart<1
					ystart=ystart-(xstart-1);
					xstart=1;
				end
			else error = 1;
			end
                elseif direction==3 
	                if sign(x1-x2)==0
	                   teken=1;
	                else teken = sign(x1-x2);
	                end
	                xstart = xstart-(teken*yp);	        	ystart = ystart-(teken*yp);	        	if inbox(xstart,ystart)
	                        xstart = xstart-SIZE/2;
	        	        ystart = ystart+SIZE/2;
				if (xstart < 1)
					ystart = ystart + (xstart-1);
					xstart = 1;
				end
	        		if (ystart > YSIZE)
					xstart = xstart + (ystart-YSIZE);
					ystart = YSIZE;
				end
			else error = 1;
			end
                end
		if (nrofpoints < maxnrofpoints) & (error == 0) & (abs(rotate) < 3)
			[x y color] = iseffil([xstart,ystart], direction, SIZE,1);
			if color == 0
			   rotate = 0;
			   addpoint(x,y);
			   nrofpoints=nrofpoints+1;
			else rotate = rotate - color;
			end    
			   
			   
	   	else
     			error = 1;
	     		seterror(' Cannot detect more points. Maybe the next point will be out of the box.');
   		end
end