Adding optipng post transformer

Imagine/Filter/PostProcessor/OptiPngPostProcessor.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace Liip\ImagineBundle\Imagine\Filter\PostProcessor;
+
+use Liip\ImagineBundle\Binary\BinaryInterface;
+use Liip\ImagineBundle\Model\Binary;
+use Symfony\Component\Process\Exception\ProcessFailedException;
+use Symfony\Component\Process\ProcessBuilder;
+
+class OptiPngPostProcessor implements PostProcessorInterface
+{
+    /** @var string Path to optipng binary */
+    protected $optipng;
+
+    /**
+     * Constructor.
+     *
+     * @param string $optipngBin Path to the optipng binary
+     */
+    public function __construct($optipngBin = '/usr/bin/optipng')
+    {
+        $this->optipngBin = $optipngBin;
+    }
+
+    /**
+     * @param BinaryInterface $binary
+     *
+     * @throws ProcessFailedException
+     *
+     * @return BinaryInterface
+     *
+     * @see      Implementation taken from Assetic\Filter\optipngFilter
+     */
+    public function process(BinaryInterface $binary)
+    {
+        $type = strtolower($binary->getMimeType());
+        if (!in_array($type, array('image/png'))) {
+            return $binary;
+        }
+
+        $pb = new ProcessBuilder(array($this->optipngBin));
+
+        $pb->add('--o7');
+        $pb->add($input = tempnam(sys_get_temp_dir(), 'imagine_optipng'));
+        file_put_contents($input, $binary->getContent());
+
+        $proc = $pb->getProcess();
+        $proc->run();
+
+        if (false !== strpos($proc->getOutput(), 'ERROR') || 0 !== $proc->getExitCode()) {
+            unlink($input);
+            throw new ProcessFailedException($proc);
+        }
+
+        $result = new Binary(file_get_contents($input), $binary->getMimeType(), $binary->getFormat());
+
+        unlink($input);
+
+        return $result;
+    }
+}

Resources/config/imagine.xml

@@ -66,9 +66,11 @@
 
         <!-- Post processors' classes -->
         <parameter key="liip_imagine.filter.post_processor.jpegoptim.class">Liip\ImagineBundle\Imagine\Filter\PostProcessor\JpegOptimPostProcessor</parameter>
-
         <parameter key="liip_imagine.jpegoptim.binary">/usr/bin/jpegoptim</parameter>
 
+        <parameter key="liip_imagine.filter.post_processor.optipng.class">Liip\ImagineBundle\Imagine\Filter\PostProcessor\OptiPngPostProcessor</parameter>
+        <parameter key="liip_imagine.optipng.binary">/usr/bin/optipng</parameter>
+
     </parameters>
 
     <services>
@@ -269,5 +271,9 @@
             <argument>%liip_imagine.jpegoptim.binary%</argument>
             <tag name="liip_imagine.filter.post_processor" post_processor="jpegoptim" />
         </service>
+        <service id="liip_imagine.filter.post_processor.optipng" class="%liip_imagine.filter.post_processor.optipng.class%">
+            <argument>%liip_imagine.optipng.binary%</argument>
+            <tag name="liip_imagine.filter.post_processor" post_processor="optipng" />
+        </service>
     </services>
 </container>

Resources/doc/filters.rst

@@ -380,3 +380,15 @@ parameters, for example:
         liip_imagine.jpegoptim.binary: /usr/local/bin/jpegoptim
 
 .. _`Symfony Service Container`: http://symfony.com/doc/current/book/service_container.html
+
+
+The ``OptiPngPostProcessor`` is also available by default and can be used just as jpegoptim. 
+Make sure that optipng binary is installed on the system and change the 
+``liip_imagine.optipng.binary`` in parameters if needed.
+
+.. code-block:: yaml
+
+    parameters:
+        liip_imagine.optipng.binary: /usr/local/bin/optipng
+
+.. _`Symfony Service Container`: http://symfony.com/doc/current/book/service_container.html