Add file transformers to the file loader

Imagine/Data/Loader/ExtendedFileSystemLoader.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Liip\ImagineBundle\Imagine\Data\Loader;
+
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+use Imagine\Image\ImagineInterface;
+
+class ExtendedFileSystemLoader extends FileSystemLoader
+{
+    /**
+     *
+     * @var array 
+     */
+    private $transformers;
+
+    /**
+     * Constructs
+     *
+     * @param ImagineInterface  $imagine
+     * @param array             $formats
+     * @param string            $rootPath
+     * @param array             $transformers
+     */
+    public function __construct(ImagineInterface $imagine, $formats, $rootPath, array $transformers)
+    {
+        parent::__construct($imagine, $formats, $rootPath);
+        $this->transformers = $transformers;
+    }
+
+    /**
+     * Apply transformers to the file
+     *
+     * @param $absolutePath
+     * @return array
+     */
+    protected function getFileInfo($absolutePath)
+    {
+        if (!empty($this->transformers)) {
+            foreach ($this->transformers as $transformer) {
+                $absolutePath = $transformer->applyTransform($absolutePath);
+            }
+        }
+        return pathinfo($absolutePath);
+    }
+}

Imagine/Data/Loader/FileSystemLoader.php

@@ -91,4 +91,4 @@ public function find($path)
 
         return $this->imagine->open($absolutePath);
     }
-}
+}

Imagine/Data/Transformer/PdfTransformer.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace Liip\ImagineBundle\Imagine\Data\Transformer;
+
+class PdfTransformer
+{
+    public function applyTransform($absolutePath)
+    {
+        $info = pathinfo($absolutePath);
+        if (isset($info['extension']) && strpos(strtolower($info['extension']), 'pdf') !== false) {
+            //Check if Imagick extension is loaded
+            if (!extension_loaded('Imagick'))
+                throw new \RuntimeException ("PHP Imagick extension is not loaded but required by the PdfTransformer");
+
+            //If it doesn't exists extract the first page of the PDF
+            if (!file_exists("$absolutePath.png")) {
+                $img = new \Imagick($absolutePath.'[0]');
+                $img->setImageFormat('png');
+                $img->writeImages($absolutePath.'.png', true);
+            }
+            //finally update $absolutePath
+            $absolutePath .= '.png';
+        }
+        return $absolutePath;
+    }
+}

README.md

@@ -383,6 +383,39 @@ liip_imagine:
 For an example of a data loader implementation, refer to
 `Liip\ImagineBundle\Imagine\Data\Loader\FileSystemLoader`.
 
+## Extending the image loader with data transformers
+
+You can extend a custom data loader to support virtually any file type using transformers.
+A data tranformer is intended to transform a file before actually rendering it. You
+can refer to `Liip\ImagineBundle\Imagine\Data\Loader\ExtendedFileSystemLoader` and
+to `Liip\ImagineBundle\Imagine\Data\Transformer\PdfTransformer` as an example.
+
+ExtendedFileSystemLoader extends FileSystemLoader and takes, as argument, an array of transformers.
+In the example, when a file with the pdf extension is passed to the data loader,
+PdfTransformer uses php imagick extension to extract the first page of the document
+and returns it to the data loader as a png image.
+
+To tell the bundle about the transformers, you have to register them as services
+with the new loader:
+
+```yml
+services:
+    acme_custom_transformer:
+        class:     Acme\ImagineBundle\Imagine\Data\Transformer\MyCustomTransformer
+    custom_loader:
+        class:     Acme\ImagineBundle\Imagine\Data\Loader\MyCustomDataLoader
+        tags:
+            -    { name: liip_imagine.data.loader, loader: custom_data_loader }
+        arguments: 
+            -    '@liip_imagine'
+            -    %liip_imagine.formats%
+            -    %liip_imagine.data_root%
+            -    [ '@acme_custom_transformer' ]
+```
+
+Now you can use your custom data loader, with its transformers, setting it
+as in the previous section.
+
 ## Custom cache resolver
 
 The ImagineBundle allows you to add your custom cache resolver classes. The only

Resources/config/imagine.xml

@@ -141,4 +141,4 @@
         </service>
 
     </services>
-</container>
+</container>