code: public function getTemplateData()
  	{
  		$rootDir = System::getContainer()->getParameter('kernel.project_dir');
  		$image = System::getContainer()->get('contao.image.image_factory')->create($rootDir . '/' . $this->image->getOriginalPath());
  
  		$config = new PictureConfiguration();
  		$config->setSize($this->getConfigurationItem($this->imageSize));
  
  		$sizeItems = array();
  
  		foreach ($this->imageSizeItems as $imageSizeItem)
  		{
  			$sizeItems[] = $this->getConfigurationItem($imageSizeItem);
  		}
  
  		$config->setSizeItems($sizeItems);
  
  		$importantPart = $this->image->getImportantPart();
  
  		$image->setImportantPart(
  			new ImportantPart(
  				new Point($importantPart['x'], $importantPart['y']),
  				new Box($importantPart['width'], $importantPart['height'])
  			)
  		);
  
  		$container = System::getContainer();
  		$staticUrl = $container->get('contao.assets.files_context')->getStaticUrl();
  
  		$picture = $container
  			->get('contao.image.picture_generator')
  			->generate(
  				$image,
  				$config,
  				(new ResizeOptions())
  					->setImagineOptions($container->getParameter('contao.image.imagine_options'))
  					->setBypassCache($container->getParameter('contao.image.bypass_cache'))
  			)
  		;
  
  		return array
  		(
  			'img' => $picture->getImg($rootDir, $staticUrl),
  			'sources' => $picture->getSources($rootDir, $staticUrl),
  		);
  	}
docs: Get the picture element definition array
  
  @return array The picture element definition