% script to interactively build polygons with

% set up window
clf
plot([-1,1,1,-1,-1], [-1,-1,1,1,-1], 'b-')
axis([-1,1,-1,1]); axis equal

% 1) input coordinates of polygon vertices with mouse
button = 1;
nverts = 1;
x = [], y = [];
while(button<4)

  plot([-1,1,1,-1,-1], [-1,-1,1,1,-1], 'b-')
  hold on
  if(nverts>1)
    scatter(x,y,'r*');
  end
  axis([-1,1,-1,1]); axis equal
  
  title('Click to select vertex (c to continue)', 'FontSize', 16)
  [xn,yn,button] = ginput(1);
  if(button<4)
    x(nverts) = xn;
    y(nverts) = yn;
    nverts = nverts+1;
  end
end
nverts = nverts-1;

% 2) select edges as pairs of vertices with mouse
edges = [];
button = 1;
while(button<4)

  plot([-1,1,1,-1,-1], [-1,-1,1,1,-1], 'b-')
  hold on
  if(nverts>1)
    scatter(x,y,'r*');
  end
  if(~isempty(edges))
    plot(x(edges)',y(edges)', 'k-')
  end

  axis([-1,1,-1,1]); axis equal

  title('choose first vertex (c to continue)', 'FontSize', 16)
  [x1,y1,button] = ginput(1);
  [mind, n1] = min( (x-x1).^2 + (y-y1).^2 );
  if(button=='c') 
    break;
  end

  hold on;
  scatter(x(n1),y(n1), 'bo', 'filled')
  hold off

  title('choose second vertex (c to continue)', 'FontSize', 16)
  [x2,y2,button] = ginput(1);
  [mind, n2] = min( (x-x2).^2 + (y-y2).^2 );
  if(button=='c') 
    break;
  end

  hold on;
  scatter(x(n2),y(n2), 'bo', 'filled')
  plot([x(n1),x(n2)],[y(n1),y(n2)], 'k-');
  hold off

  title('space bar to reject, a to accept, c to continue', 'FontSize', 16)

  [foo,bah,button] = ginput(1);
  if(button==' ')
    
  end
  if(button=='a' || button=='c')
    [n1,n2]
    edges = [edges;[n1,n2]]
  end
  if(button=='c')
    break;
  end
  button = 0;
end


% 3) choose edges that form polygon with mouse
nedges = size(edges, 1);

polyg = [];
button = 1;
while(button<4)

  plot([-1,1,1,-1,-1], [-1,-1,1,1,-1], 'b-')
  hold on
  scatter(x,y,'r*');
  plot(x(edges),y(edges), 'k-')
  if(~isempty(polyg))
    plot(x(edges(polyg,:))',y(edges(polyg,:))', 'b-')'
  end
  hold off
  axis([-1,1,-1,1]); axis equal

  title('choose edge (c to continue)', 'FontSize', 16)
  [mx,my,button] = ginput(1);
  mx = [mx;my];

  ab = zeros(size(edges,1),1);
  for e=1:size(edges,1)
    v1 = edges(e,1);
    v2 = edges(e,2);
    x1 = [x(v1);y(v1)];
    x2 = [x(v2);y(v2)];
    b = dot(mx-x1,x2-x1)/norm(x2-x1)^2;
    b = max(min(b,1),0);
    ab(e) = norm( mx - (x1 + b*(x2-x1)) );
  end

  [mind, e] = min( ab );
  if(button=='c') 
    break;
  end

  hold on
  plot(x(edges(e,:))',y(edges(e,:))', 'b-')
  hold off

  title('a Accept (c to continue)', 'FontSize', 16)
  [foo,bah,button] = ginput(1);
  if(button=='a')
    polyg = [polyg;e];
  end
  if(button=='c')
    break;
  end
  button = 0;
  
  pause(.04)
end

% 4) select point inside polygon with mouse
button = 'b';
while(button~='a')
  title('select point inside polygon', 'FontSize', 16)
  [xin,yin] = ginput(1);
  hold on
  scatter(xin,yin, 'k*');

  title('a accept', 'FontSize', 16);
  [foo,bah,button] = ginput(1);
end

% 5) output polygon to .poly formatted file
fname = input('filename: ', 's');

fid = fopen(fname, 'w');

fprintf(fid, '# %s example \n', fname);
fprintf(fid, '# Number of vertices\n');
fprintf(fid, '%d \n', nverts);
fprintf(fid, '# Vertex descriptions [vertex number, x coordinate, y coordinate]\n');
for n=1:nverts
fprintf(fid, '%d %f %f\n', n, x(n),y(n));
end

fprintf(fid, '# Number of edges \n');
fprintf(fid, '%d\n', nedges);
fprintf(fid, '# Edge descriptions [edge number, first vertex, second vertex]\n');
for n=1:nedges
 fprintf(fid, '%d %d %d \n', n, edges(n,1), edges(n,2));
end

fprintf(fid, '# Number of edges in polygon \n');
fprintf(fid, '%d\n', length(polyg));
fprintf(fid, '# Polygon description [ list of edges ]\n');
for n=1:length(polyg)
fprintf(fid, '%d ', polyg(n));
end
fprintf(fid, '\n');
fprintf(fid, '# Point inside polygon [ x coordinate, y coordinate ]\n');
fprintf(fid, '%f %f\n', xin,yin);

fclose(fid);