system/Images/Handlers/BaseHandler.php
public function flip(string $dir = 'vertical')
	{
		$dir = strtolower($dir);

		if ($dir !== 'vertical' && $dir !== 'horizontal')
		{
			throw ImageException::forInvalidDirection($dir);
		}

		return $this->_flip($dir);
	}
public function flip(string $dir = 'vertical')
	{
		$dir = strtolower($dir);

		if ($dir !== 'vertical' && $dir !== 'horizontal')
		{
			throw ImageException::forInvalidDirection($dir);
		}

		return $this->_flip($dir);
	}
Flips an image either horizontally or vertically.

@param string $dir Either 'vertical' or 'horizontal'

@return $this