RWP in Timber theme

<?php
function timber_get_film_strip_image( $id = null, $caption = '', $class = '') {
    $markup = '';

    //do nothing if we have no ID
    if ( empty( $id ) ) {
        return $markup;
    }

    if ( empty( $caption ) ) {
        //try to get the caption from the attachment metadata
        $caption = timber_get_img_caption( $id );
    }
    $image_full_size = wp_get_attachment_image_src( $id, 'full' );
    $image_small_size = wp_get_attachment_image_src( $id, 'timber-small-image' );
    $image_large_size = wp_get_attachment_image_src( $id, 'timber-large-image' );

    //get directly the raw metadata because Jetpack Photon ruins stuff for us - no dimensions are returned by wp_get_attachment_image_src()
    $image_data = wp_get_attachment_metadata( $id );

    $markup .=
    '<div class="portfolio__item js-placeholder js-portfolio-item  proof-photo ' . $class . '"
        id="' . $id . '"
        data-attachment_id="' . $id . '"
        data-alt="' . esc_attr( timber_get_img_alt( $id ) ) . '"
        data-caption="' . esc_attr( $caption ) . '"
        data-description="' . esc_attr( timber_get_img_description( $id ) ) . '"
        data-exif="' . esc_attr( timber_get_img_exif( $id ) ) . '"
        data-width="' . $image_data["width"] . '"
        data-height="' . $image_data["height"] . '">

        '.rwp_img( $id ).'

        <div class="proof__overlay">
            <button class="proof-btn  proof-btn--thumbs  js-thumbs"></button>
            <button class="proof-btn  proof-btn--zoom  js-zoom"></button>
            <button data-photoid="' . $id . '" class="proof-btn  proof-btn--plus  js-plus  select-action"></button>
            <button data-photoid="' . $id . '" class="proof-btn  proof-btn--minus  js-plus  select-action"></button>
        </div>
        <div class="proof__selected"></div>

        <noscript>
            <img src="' . $image_small_size[0] . '" alt="' . esc_attr( timber_get_img_alt( $id ) ) . '" width="' . $image_small_size[1] . '" height="' . $image_small_size[2] . '">
        </noscript>
    </div><!-- .portfolio__item -->' . PHP_EOL;

    return $markup;
}
?>