imagemagick pdf未转换为图像

<?php 
class Pdf_to_img extends CI_Controller{
public function converter(){
$this->load->library('image_lib');
$config = array(
    'image_library' => 'imagemagick',
    'library_path' => 'D:\Program Files\ImageMagick-6.9.3-Q16',
    'source_image' => 'theme/assets/pdf/ci.pdf' ,
    'new_image' => 'theme/assets/img/copy.jpg' ,
    'maintain_ratio' => true,
    'width' => 980,
    'quality' => '90%',
   );

   $this->image_lib->initialize( $config );

   if ( $this->image_lib->resize( ) ) {
    $this->image_lib->clear( );
   }
 }
 }
 ?>

Friends as i'm new to codeigniter , i'm converting a pdf file into image while surfing i've got this piece of code i've altered all the location but while executing i'm recieving the error as

The path to the image is not correct. Image processing failed. Please verify that your server supports the chosen protocol and that the path to your image library is correct.

So please correct my code if there is any error or any code to be added to make the change

I've installed the ImageMagick ON D:\Program Files\ImageMagick-6.9.3-Q16

and source_image path is D:\wamp\www\login\theme\assets\pdf

and new image path is D:\wamp\www\login\theme\assets\img

Please verify that the imagickphp library is installed first. Then uses the following commands:

$imagick = new Imagick();
$imagick->readImage('mytest.pdf');
$imagick->writeImage('output.jpg');