function grayscaleImageIE(imgObj)
{
  imgObj.style.filter = 'progid:DXImageTransform.Microsoft.BasicImage(grayScale=1)';
}

function grayscaleImage(imgObj)
{
  var canvas = document.createElement('canvas');
  var canvasContext = canvas.getContext('2d');
        
  var imgW = imgObj.width;
  var imgH = imgObj.height;
  canvas.width = imgW;
  canvas.height = imgH;
        
  canvasContext.drawImage(imgObj, 0, 0);
  var imgPixels = canvasContext.getImageData(0, 0, imgW, imgH);
        
  for(var y = 0; y < imgPixels.height; y++){
    for(var x = 0; x < imgPixels.width; x++){
      var i = (y * 4) * imgPixels.width + x * 4;
      var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
      imgPixels.data[i] = avg; 
      imgPixels.data[i + 1] = avg; 
      imgPixels.data[i + 2] = avg;
    }
  }
        
  canvasContext.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
  return canvas.toDataURL();
}