Magento 2 Error – Unable to Write File into Directory

Someone solve this with permission 644 files and 755 on folders

Others rename their .htacess file to .htacess-old and checked if the problem persist

I just updated to Magento 2.1.6 on Windows and had this same issue. I did a little searching and came across a post on Github here.

In a nutshell you need to do two things in vendor/magento/module-catalog/Model/View/Asset/Image.php.

The first thing is replace all occurrences of DIRECTORY_SEPARATOR with '/'

The second is edit the getRelativePath function to look like:

private function getRelativePath($result)
{
    $prefix = $result == '/' ? $result : '';
    $result = $this->join($result, $this->getModule());
    $result = $this->join($result, $this->getMiscPath());
    $result = $this->join($result, $this->getFilePath());
    return $prefix . $result;
}

You need both changes or it won't work. Just replacing DIRECTORY_SEPARATOR still throws a forbidden error. Not including the $prefix elements in getRelativePath causes the forbidden error to go away, but product images won't load.