//Edit cart price
add_action( 'woocommerce_before_calculate_totals', 'add_custom_price', 99 );
function add_custom_price( $cart_object ) {

  foreach ( $cart_object->cart_contents as $key => $value ) {

    $variation = new \WC_Product_Variation( $value['variation_id'] );
    $variation_price_per_m2 = $variation->get_price();


    if ( isset( $value[ 'fotolia_id' ] ) ) {
      $image_area = floatval( $value['image_area'] );

      $fotolia_photo_price = floatval( $value['fotolia_photo_price'] );

      $new_price = $variation_price_per_m2 * $image_area + $fotolia_photo_price;

    } else if ( isset( $value[ 'image_filename' ] ) ) {
      $image_area = floatval( $value['image_area'] );

      $new_price = $variation_price_per_m2 * $image_area;

    } else {
      $id = $value['data']->get_id();

      $product_price_per_m2 = $value['data']->get_price();

      $new_price = intval( $value[ 'image_width' ] ) * intval( $value[ 'image_height' ] ) / 10000 * $product_price_per_m2;

    }

    $value['data']->set_price( $new_price );
  }
}