[WOOCOMMERCE] Get category thumbnail without resize

functions.php

<?php
/*
 * @goliver: overwrite function for get category thumbnail size without resize
 * original in woocommerce-template.php
 */
function woocommerce_subcategory_thumbnail( $category ) {
    global $woocommerce;

    $small_thumbnail_size  	= apply_filters( 'single_product_small_thumbnail_size', 'shop_catalog' );
    $dimensions    		= $woocommerce->get_image_size( $small_thumbnail_size  );
    $thumbnail_id  		= get_woocommerce_term_meta( $category->term_id, 'thumbnail_id', true  );

    if ( $thumbnail_id ) {
        $image = wp_get_attachment_image_src( $thumbnail_id, 'post-thumbnail'  );
        $image = $image[0];
    } else {
        $image = woocommerce_placeholder_img_src();
    }

    if ( $image )
        echo '<img src="' . $image . '" alt="' . $category->name . '" />';
}