Can't change image attribute src I want use Lazy Load jQuery Plugin. So, I must change image src to data-original path.

&lt;img class="field-slideshow-image field-slideshow-image-1 image-style-slides" 
typeof="foaf:Image" src="/sites/all/themes/mytheme/images/myimg.png" 
width="490" height="370" alt="" title="" style=""&gt;


And I added this code to my template.php:

function mytheme_preprocess_image(&amp;$variables) {
   if ($variables['style_name'] == 'slides') {
       $variables['attributes']['class'][] = 'lazy';
       $variables['attributes']['data-original'][] = file_create_url($variables['path']);
       $variables['path'] = '/sites/all/themes/mytheme/images/grey.png';
   }
}


Yes, this code add data-original attribute. But not add grey.png image to src

&lt;img class="field-slideshow-image field-slideshow-image-1 image-style-slides 
lazy" typeof="foaf:Image" data-
original="mytheme/files/styles/slides/public/slides/myimg.png" src="/sites/all/themes/mytheme/images/myimg.png" 
width="490" height="370" alt="" title="" style=""&gt;


What's problem? How can I fix it? Thanks.
function mytheme_preprocess_image(&amp;$variables) {
   if ($variables['style_name'] == 'slides') {
       $variables['attributes']['data-original'][] = file_create_url($variables['path']);
       $variables['attributes']['class'][] = 'lazy';
       $variables['path'] = '/sites/all/themes/mytheme/images/grey.png';
   }
}


Regards