Display image in codeigniter datatable - ajax

Question

Controller : here productlist2() just call the view page .
function productlist2()
{
$this->load->view("admin/bill/datatable.php", array());
}
public function productlist_page()
{
$draw = intval($this->input->get("draw"));
$start = intval($this->input->get("start"));
$length = intval($this->input->get("length"));
$books = $this->Category_model->get_all_product_datatable();
$data = array();
foreach($books->result() as $r) {
$data[] = array(
$r->categoryID,
$r->productName,
$r->costPrice,
$r->salesPrice,
$r->unit,
$r->origin,
$r->files
);
}
$output = array(
"draw" => $draw,
"recordsTotal" => $books->num_rows(),
"recordsFiltered" => $books->num_rows(),
"data" => $data
);
echo json_encode($output);
exit();
}
After ajax calling the productlist_page() function this productlist_page() gets the value from model.
View:
<table id="book-table" class="table table-bordered table-striped table-hover">
<thead>
<tr>
<td>ID</td>
<td>Product Name</td>
<td>Cost Price</td>
<td>Sales Price</td>
<td>Unit</td>
<td>Description</td>
<td>Picture</td>
</tr>
</thead>
<tbody>
</tbody>
</table>
Here is my js script code.
<script type="text/javascript">
$(document).ready(function() {
$('#book-table').DataTable({
"ajax": {
url : "<?php echo site_url("admin/category/productlist_page") ?>",
type : 'GET'
},
});
});
</script>
Here , in picture column i want to show images , only the string value is there as output in files column . Question is how can i show the image ?