Reflect images

The JavaScript code

Here is the complete code to accomplish this behaviour.

(function(){
  var brd = JXG.JSXGraph.initBoard('jxgbox', {boundingbox:[-5,5,13,-2.5], grid:true});
  var p0, p1, p2, p3, p5,
      l1, l2,
      im1, im2, im3, 
      t1, t2,
      imurl = "/distrib/images/uccellino.jpg",
      X, Y, W, H;          // Functions defining the position, width and height of the original image.

  // Define two line through four points
  p0 = brd.create('point', [2,-2]); 
  p1 = brd.create('point', [2,1]); 
  p2 = brd.create('point', [10,-1]); 

  l1 = brd.create('line', [p0, p1]); 
  l2 = brd.create('line', [p1, p2]); 

  p4 = brd.create('point', [-2,-2]); 
  p5 = brd.create('point', [1,0]); 

  X = function(){ return Math.min(p4.X(), p5.X()); };
  Y = function(){ return Math.min(p4.Y(), p5.Y()); };
  W = function(){ return Math.abs(p5.X() -p4.X()); };
  H = function(){ return Math.abs(p5.Y() -p4.Y()); };

  im1 = brd.create('image',[imurl, [X, Y], [W, H]], {opacity:0.7}); 
  im2 = brd.create('image',[imurl, [X, Y], [W, H]], {opacity:0.7}); 
  im3 = brd.create('image',[imurl, [X, Y], [W, H]], {opacity:0.7}); 

  t1 = brd.create('transform', [l1], {type:'reflect'});
  t2 = brd.create('transform', [l2], {type:'reflect'});

  // Reflect im2 on l1
  t1.bindTo(im2);

  // Reflect im3 on l1 and on l2
  t1.bindTo(im3);
  t2.bindTo(im3);

  brd.update();

})();