$('div a.grid-image').map(function (i, link){
  $('body').append('<canvas/>');
  var canvas = $('canvas')[i];

  var ctx = canvas.getContext('2d');
  var img = new Image();
  img.crossOrigin = 'anonymous';
  img.src = '...';
  img.onload = function(){
      ctx.drawImage(img, 0, 0);
  };

  img.src = link.href;

  var filename = $(link).attr('title');
  link.href = img.src;
  link.download = filename + '.png';
  link.click();

});