Image upload in magento 2

<?php
namespace Bharat\Bannerslider\Controller\Adminhtml\Bannerslider;
use Magento\Framework\App\Filesystem\DirectoryList;

class Save extends \Magento\Backend\App\Action 
{
    protected $resultRawFactory;
    public function __construct(  
        \Magento\Backend\App\Action\Context $context
    ) {
        parent::__construct($context);
    }

    public function execute()
    {        
        try
        {       
            $uploader = $this->_objectManager->create('Magento\MediaStorage\Model\File\Uploader',['fileId' => 'image']);
            $uploader->setAllowedExtensions(['jpg', 'jpeg', 'gif', 'png']);
            $imageAdapter = $this->_objectManager->get('Magento\Framework\Image\AdapterFactory')->create();
            $uploader->addValidateCallback('image', $imageAdapter, 'validateUploadFile');
            $uploader->setAllowRenameFiles(true);
            $uploader->setFilesDispersion(true);
            
            $mediaDirectory = $this->_objectManager->get('Magento\Framework\Filesystem')->getDirectoryRead(DirectoryList::MEDIA);
            $config = $this->_objectManager->get('Magento\Catalog\Model\Product\Media\Config');
            $pth = $mediaDirectory->getAbsolutePath('Bannerslider/images');
            $result = $uploader->save($mediaDirectory->getAbsolutePath('Bannerslider/images'));
            $imgpath = $this->_prepareFile($result['file']);
            $imgpathArray = explode("/", $imgpath);
            unset($imgpathArray[count($imgpathArray)-1]);
            $imgpath = implode("/", $imgpathArray);
            $this->chmod_r($result['path'].'/' . $imgpath);
            chmod($result['path'].'/' .$this->_prepareFile($result['file']), 0777);
            unset($result['tmp_name']);
            unset($result['path']);
            $url = $this->_objectManager->get('Magento\Framework\UrlInterface')->getBaseUrl().$this->getBaseMediaUrlAddition();
            $result['url'] =   $url . '/' . $this->_prepareFile($result['file']);
            $result['file'] = $result['file'];
        }
        catch(\Exception $e)
        {
            $result = ['error' => $e->getMessage(), 'errorcode' => $e->getCode()];
        }
        $response = $this->_objectManager->get('Magento\Framework\Controller\Result\RawFactory')->create();
        $response->setHeader('Content-type', 'text/plain');
        $response->setContents(json_encode($result));
        return $response;
    }

    private function chmod_r($path) {
        $dir = new \DirectoryIterator($path);
        foreach ($dir as $item) {
        chmod($item->getPathname(), 0777);
            if ($item->isDir() && !$item->isDot()) {
                chmod_r($item->getPathname());
            }
        }
    }

    private function getBaseMediaUrlAddition()
    {
        return 'pub/media/Bannerslider/images';
    }

    private function _prepareFile($file)
    {
    return ltrim(str_replace('\\', '/', $file), '/');
    }
}