Remove accents, lowercase and underscores to dashes

functions.php

<?php

add_filter( 'sanitize_file_name', 'themename_sanitize_file_name' );
/**
 * Remove accents, maybe lowercase and underscores to dashes
 *
 * @version 1.0.4
 * @link https://gist.github.com/camaleaun/d8d12d04ff879a89d833c9eb39362eda
 * @param string $filename Name of file.
 * @return string Sanitized file name.
 */
function themename_sanitize_file_name( $filename ) {
	$filename   = remove_accents( $filename );
	$filename   = preg_replace( '|%[a-fA-F0-9][a-fA-F0-9]|', '', $filename );
	$filename   = preg_replace( '/[^A-Za-z0-9._-]/', '', $filename );
	$check_file = wp_check_filetype( $filename );
	$ext        = $check_file['ext'];
	$filename   = preg_replace( "/\.$ext$/", '', $filename );
	preg_match( '/[\d\.]+/', $filename, $dotnumber );
	if ( ! empty( $dotnumber ) ) {
		$dotnumber = current( $dotnumber );
		$filename = preg_replace( "/$dotnumber/", str_replace( '.', '', $dotnumber ), $filename );
	}
	preg_match_all( '/[a-zA-Z]*/', $filename, $letters );
	$letters = implode( '', array_filter( $letters[0] ) );
	if ( ctype_upper( $letters ) ) {
		$filename = strtolower( $filename );
	}
	$filename  = str_replace( '.', '-', $filename );
	$filename  = str_replace( '_', '-', $filename );
	$filename  = preg_replace( '/-+/', '-', $filename );
	$filename .= '.' . strtolower( $ext );
	return $filename;
}