Creation of a Gif Media to be able to extract gif animation based on video sequences (#285)

* Creation of a media to extract video sequences into gif files
* We add a gif method to the class Video to be able to use the Gif Media.
* Parameters where missing in the declaration of the gif function
* One parameter was badly defined in the gif method
* We use the proper media in the method gif
* We add a missing declaration in the Video class
* Update of the README file
* Modification of the README file
* We remove an empty class

src/FFMpeg/Filters/Gif/GifFilterInterface.php

@@ -0,0 +1,20 @@
+<?php
+
+/*
+ * This file is part of PHP-FFmpeg.
+ *
+ * (c) Strime <contact@strime.io>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FFMpeg\Filters\Gif;
+
+use FFMpeg\Filters\FilterInterface;
+use FFMpeg\Media\Gif;
+
+interface GifFilterInterface extends FilterInterface
+{
+    public function apply(Gif $gif);
+}

src/FFMpeg/Filters/Gif/GifFilters.php

@@ -0,0 +1,24 @@
+<?php
+
+/*
+ * This file is part of PHP-FFmpeg.
+ *
+ * (c) Strime <contact@strime.io>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FFMpeg\Filters\Gif;
+
+use FFMpeg\Media\Gif;
+
+class GifFilters
+{
+    private $gif;
+
+    public function __construct(Gif $gif)
+    {
+        $this->gif = $gif;
+    }
+}

src/FFMpeg/Media/Gif.php

@@ -0,0 +1,137 @@
+<?php
+
+/*
+ * This file is part of PHP-FFmpeg.
+ *
+ * (c) Strime <contact@strime.io>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FFMpeg\Media;
+
+use Alchemy\BinaryDriver\Exception\ExecutionFailureException;
+use FFMpeg\Filters\Gif\GifFilterInterface;
+use FFMpeg\Filters\Gif\GifFilters;
+use FFMpeg\Driver\FFMpegDriver;
+use FFMpeg\FFProbe;
+use FFMpeg\Exception\RuntimeException;
+use FFMpeg\Coordinate\TimeCode;
+use FFMpeg\Coordinate\Dimension;
+
+class Gif extends AbstractMediaType
+{
+    /** @var TimeCode */
+    private $timecode;
+    /** @var Dimension */
+    private $dimension;
+    /** @var integer */
+    private $duration;
+    /** @var Video */
+    private $video;
+
+    public function __construct(Video $video, FFMpegDriver $driver, FFProbe $ffprobe, TimeCode $timecode, Dimension $dimension, $duration = null)
+    {
+        parent::__construct($video->getPathfile(), $driver, $ffprobe);
+        $this->timecode = $timecode;
+        $this->dimension = $dimension;
+        $this->duration = $duration;
+        $this->video = $video;
+    }
+
+    /**
+     * Returns the video related to the gif.
+     *
+     * @return Video
+     */
+    public function getVideo()
+    {
+        return $this->video;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @return GifFilters
+     */
+    public function filters()
+    {
+        return new GifFilters($this);
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @return Gif
+     */
+    public function addFilter(GifFilterInterface $filter)
+    {
+        $this->filters->add($filter);
+
+        return $this;
+    }
+
+    /**
+     * @return TimeCode
+     */
+    public function getTimeCode()
+    {
+        return $this->timecode;
+    }
+
+    /**
+     * @return Dimension
+     */
+    public function getDimension()
+    {
+        return $this->dimension;
+    }
+
+    /**
+     * Saves the gif in the given filename.
+     *
+     * @param string  $pathfile
+     *
+     * @return Gif
+     *
+     * @throws RuntimeException
+     */
+    public function save($pathfile)
+    {
+        /**
+         * @see http://ffmpeg.org/ffmpeg.html#Main-options
+         */
+        $commands = array(
+            '-ss', (string)$this->timecode
+        );
+
+        if(null !== $this->duration) {
+            $commands[] = '-t';
+            $commands[] = (string)$this->duration;
+        }
+
+        $commands[] = '-i';
+        $commands[] = $this->pathfile;
+        $commands[] = '-vf';
+        $commands[] = 'scale=' . $this->dimension->getWidth() . ':-1';
+        $commands[] = '-gifflags';
+        $commands[] = '+transdiff';
+        $commands[] = '-y';
+
+        foreach ($this->filters as $filter) {
+            $commands = array_merge($commands, $filter->apply($this));
+        }
+
+        $commands = array_merge($commands, array($pathfile));
+
+        try {
+            $this->driver->command($commands);
+        } catch (ExecutionFailureException $e) {
+            $this->cleanupTemporaryFile($pathfile);
+            throw new RuntimeException('Unable to save gif', $e->getCode(), $e);
+        }
+
+        return $this;
+    }
+}

src/FFMpeg/Media/Video.php

@@ -13,6 +13,7 @@ namespace FFMpeg\Media;
 
 use Alchemy\BinaryDriver\Exception\ExecutionFailureException;
 use FFMpeg\Coordinate\TimeCode;
+use FFMpeg\Coordinate\Dimension;
 use FFMpeg\Filters\Audio\SimpleFilter;
 use FFMpeg\Exception\InvalidArgumentException;
 use FFMpeg\Exception\RuntimeException;
@@ -181,4 +182,17 @@ class Video extends Audio
     {
         return new Frame($this, $this->driver, $this->ffprobe, $at);
     }
+
+    /**
+     * Extracts a gif from a sequence of the video.
+     *
+     * @param  TimeCode $at
+     * @param  Dimension $dimension
+     * @param  integer $duration
+     * @return Gif
+     */
+    public function gif(TimeCode $at, Dimension $dimension, $duration = null)
+    {
+        return new Gif($this, $this->driver, $this->ffprobe, $at, $dimension, $duration);
+    }
 }