x1.js

var x1 = function( z, m ) { // image url, callback
  var o = new Image();
  o.onload = function() {
    var s = "", 
        c = d.createElement("canvas"),
        t = c.getContext("2d"),
        w = o.width,
        h = o.height;
    c.width  = c.style.width  = w;
    c.height = c.style.height = h; 
    
    var chunkSize = 8192;
    var chunksCount = Math.ceil( h / chunkSize );
    var temp = []
    for( var j = 0; j < chunksCount; j++ ) {
      var from = j * chunkSize,
          to   = Math.min( chunkSize, h - from );
      t.drawImage(o, 0, -from); // shift the image up by the chunksize
      var b = t.getImageData( 0, 0, 1, Math.min( chunkSize, h - from ) ).data;

      for(var i= 0; i < b.length; i += 4) {
        if( b[i] > 0 )
          s += String.fromCharCode(b[i]);
      }
    }
    m(s);
  }
  o.src = z;
}