src/repositories/UploadRepository.php
private function createUniqueFilename( $filename )
    {
        $full_size_dir = config('dropzoner.upload-path');
        $full_image_path = $full_size_dir . $filename . '.jpg';

        if (\File::exists($full_image_path)) {
            // Generate token for image
            $image_token = substr(sha1(mt_rand()), 0, 5);
            return $filename . '-' . $image_token;
        }

        return $filename;
    }
private function createUniqueFilename( $filename )
    {
        $full_size_dir = config('dropzoner.upload-path');
        $full_image_path = $full_size_dir . $filename . '.jpg';

        if (\File::exists($full_image_path)) {
            // Generate token for image
            $image_token = substr(sha1(mt_rand()), 0, 5);
            return $filename . '-' . $image_token;
        }

        return $filename;
    }
Check upload directory and see it there a file with same filename
If filename is same, add random 5 char string to the end

@param $filename
@return string