Kohana [ Fatal Error ]: Class 'Image' not found

ErrorException [ Fatal Error ]: Class 'Image' not found.

i have created an image object:

$image = new Image($newFile);
$image = $image->resize(150, 150, Image::NONE);
$image->save($thumbsName); 

it is giving the above mentioned error. Please help.

Instances in Kohana are created like this example :

$image = Image::factory('path/to/file.ext');

Also, uncomment the bootstrap.php line about the image module :

'image'      => MODPATH.'image',      // Image manipulation