Initials Avatars Instead of Gravatar

add_filter( 'pre_get_avatar', function ( $html, $id_or_email, $args ) {
    if ( null !== $html || ( empty( $args['force_display'] ) && ! get_option( 'show_avatars' ) ) ) {
        return $html;
    }

    $name = '';

    if ( $id_or_email instanceof WP_Comment ) {
        $name = $id_or_email->user_id ? get_the_author_meta( 'display_name', $id_or_email->user_id ) : $id_or_email->comment_author;
    } elseif ( $id_or_email instanceof WP_User ) {
        $name = $id_or_email->display_name;
    } elseif ( $id_or_email instanceof WP_Post ) {
        $name = get_the_author_meta( 'display_name', $id_or_email->post_author );
    } elseif ( is_numeric( $id_or_email ) ) {
        $name = get_the_author_meta( 'display_name', (int) $id_or_email );
    } elseif ( is_string( $id_or_email ) ) {
        $user = get_user_by( 'email', $id_or_email );
        $name = $user ? $user->display_name : strtok( $id_or_email, '@' );
    }

    $name     = trim( (string) $name );
    $parts    = preg_split( '/[\s._-]+/u', $name, -1, PREG_SPLIT_NO_EMPTY );
    $initials = '';

    foreach ( array_slice( (array) $parts, 0, 2 ) as $part ) {
        $initials .= function_exists( 'mb_substr' ) ? mb_strtoupper( mb_substr( $part, 0, 1 ) ) : strtoupper( substr( $part, 0, 1 ) );
    }

    $initials = '' !== $initials ? $initials : '?';
    $hue      = abs( crc32( $name ) ) % 360;
    $width    = (int) ( ! empty( $args['width'] ) ? $args['width'] : $args['size'] );
    $height   = (int) ( ! empty( $args['height'] ) ? $args['height'] : $args['size'] );

    $svg = sprintf(
        '<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100" viewBox="0 0 100 100"><rect width="100" height="100" fill="hsl(%d,45%%,45%%)"/><text x="50" y="50" dy=".35em" text-anchor="middle" font-family="Arial,Helvetica,sans-serif" font-size="42" fill="#fff">%s</text></svg>',
        $hue,
        htmlspecialchars( $initials, ENT_QUOTES | ENT_XML1, 'UTF-8' )
    );

    $class = array( 'avatar', 'avatar-' . (int) $args['size'], 'photo' );
    if ( ! empty( $args['class'] ) ) {
        $class = array_merge( $class, (array) $args['class'] );
    }

    return sprintf(
        '<img alt="%1$s" src="%2$s" class="%3$s" height="%4$d" width="%5$d" %6$s>',
        esc_attr( $args['alt'] ),
        esc_attr( 'data:image/svg+xml;base64,' . base64_encode( $svg ) ),
        esc_attr( implode( ' ', $class ) ),
        $height,
        $width,
        isset( $args['extra_attr'] ) ? $args['extra_attr'] : ''
    );
}, 10, 3 );