Add and use jquery.getimagedata.min.js

Hi

i need to use jquery.getimagedata.min.js to do this : http://webdesignerwall.com/tutorials/html5-grayscale-image-hover

so i copied jquery.getimagedata.min.js in the jquery plugins module folder and added this in the bottom of my page-custom.tpl.php :

<?php
jquery_plugin_add('getimagedata');
?>

but still error :

Index or size is negative or greater than the allowed amount" code: "1
var imgPixels = ctx.getImageData(0, 0, canvas.width, canvas.height); 
Index or size is negative or greater than the allowed amount"  code: "1
http://caucadis.dev/sites/all/themes/Cyrano_CA/js/grayscale_hover.js
Line 42

whats wrong ?
thanks