Add Spectrum audio filter

tests/Functional/AudioImagingTest.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Tests\FFMpeg\Functional;
+
+use FFMpeg\FFMpeg;
+use FFMpeg\FFProbe;
+use FFMpeg\Media\Spectrum;
+
+class AudioImagingTest extends FunctionalTestCase
+{
+    /**
+     * Path prefix to avoid conflicts with another tests.
+     */
+    const OUTPUT_PATH_PREFIX = 'output/audio_';
+
+    public function testgenerateSpectrumImage()
+    {
+        $ffmpeg = FFMpeg::create();
+        $ffprobe = FFProbe::create();
+        $audio = $ffmpeg->open(realpath(__DIR__ . '/../files/Audio.mp3'));
+        $spectrum = new Spectrum($audio, $ffmpeg->getFFMpegDriver(), $ffprobe, 1024, 1024);
+        $spectrum->setLegend(false)
+            ->setOrientation('horizontal')
+            ->setColor('fiery');
+        $output = __DIR__ . '/' . self::OUTPUT_PATH_PREFIX . 'spectrum.png';
+        $spectrum->save($output);
+        $this->assertFileExists($output);
+        unlink($output);
+    }
+}

tests/Unit/Media/SpectrumTest.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Tests\FFMpeg\Unit\Media;
+
+use FFMpeg\Media\Spectrum;
+
+class SpectrumTest extends AbstractMediaTestCase
+{
+
+    /**
+     * @dataProvider provideSaveOptions
+     */
+    public function testSave($commands)
+    {
+        $driver = $this->getFFMpegDriverMock();
+        $ffprobe = $this->getFFProbeMock();
+
+        $pathfile = '/tests/files/Audio.mp3';
+
+        array_push($commands, $pathfile);
+
+        $driver->expects($this->once())
+            ->method('command')
+            ->with($commands);
+
+        $spectrum = new Spectrum($this->getAudioMock(), $driver, $ffprobe, 640, 120);
+        $this->assertSame($spectrum, $spectrum->save($pathfile));
+    }
+
+    public function provideSaveOptions()
+    {
+        return array(
+            array(
+                array(
+                    '-y', '-i', NULL, '-filter_complex',
+                    'showspectrumpic=s=640x120',
+                    '-frames:v', '1',
+                ),
+            ),
+        );
+    }
+}