Bolt\Twig\Handler\ImageHandler::showImage PHP Method

    public function showImage($fileName = null, $width = null, $height = null, $crop = null)
    {
        if (empty($fileName)) {
            return '';
        }
        $thumb = $this->getThumbnail($fileName, $width, $height, $crop);
        if ($width === null && $height === null) {
            $thumbconf = $this->app['config']->get('general/thumbnails');
            $width = !empty($thumbconf['default_image'][0]) ? $thumbconf['default_image'][0] : 1000;
            $height = !empty($thumbconf['default_image'][1]) ? $thumbconf['default_image'][1] : 750;
            $thumb->setWidth($width);
            $thumb->setHeight($height);
        } elseif ($width === null xor $height === null) {
            $info = $this->imageInfo($thumb->getFileName(), false)->getInfo();
            if ($width !== null) {
                $width = min($width, $info->getWidth());
                $thumb->setHeight(round($width / $info->getAspectRatio()));
            } elseif ($height !== null) {
                $height = min($height, $info->getHeight());
                $thumb->setWidth(round($height * $info->getAspectRatio()));
            } else {
                $thumb->setWidth($info->getWidth());
                $thumb->setHeight($info->getHeight());
            }
        }
        return sprintf('<img src="%s" width="%s" height="%s" alt="%s">', $this->getThumbnailUri($thumb), $thumb->getWidth(), $thumb->getHeight(), $thumb->getAltTitle());
    }

 public function testShowImageFileNameArrayWithAlt()
 {
     $app = $this->getApp();
     $handler = new ImageHandler($app);
     $result = $handler->showImage(['title' => 'Koala', 'alt' => 'Gum Leaves', 'filename' => 'generic-logo.png'], null, null, null, null);
     $this->assertSame('<img src="/thumbs/1000x750c/generic-logo.png" width="1000" height="750" alt="Gum Leaves">', $result);
 }