added custom frame filter

src/FFMpeg/Filters/Frame/CustomFrameFilter.php

@@ -0,0 +1,54 @@
+<?php
+
+/*
+ * This file is part of PHP-FFmpeg.
+ *
+ * (c) Alchemy <dev.team@alchemy.fr>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FFMpeg\Filters\Frame;
+
+use FFMpeg\Exception\RuntimeException;
+use FFMpeg\Media\Frame;
+
+class CustomFrameFilter implements FrameFilterInterface
+{
+    /** @var string */
+    private $filter;
+    /** @var integer */
+    private $priority;
+
+    /**
+     * A custom filter, useful if you want to build complex filters
+     *
+     * @param string $filter
+     * @param int    $priority
+     */
+    public function __construct($filter, $priority = 0)
+    {
+        $this->filter = $filter;
+        $this->priority = $priority;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getPriority()
+    {
+        return $this->priority;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function apply(Frame $frame)
+    {
+        $commands = array('-vf', $this->filter);
+
+        return $commands;
+    }
+}
+

src/FFMpeg/Filters/Frame/FrameFilters.php

@@ -36,4 +36,18 @@ class FrameFilters
 
         return $this;
     }
+
+    /**
+     * Applies a custom filter: -vf foo bar
+     *
+     * @param string    $parameters
+     *
+     * @return FrameFilters
+     */
+    public function custom($parameters)
+    {
+        $this->frame->addFilter(new CustomFrameFilter($parameters));
+
+        return $this;
+    }
 }