Default woocommerce placeholder image

The code for changing the default image is provided by WooCommerce in this link
but for your requirement we have to customize the code as follows

    /*
    * goes in theme functions.php or a custom plugin. Replace the image filename/path with your own :)
    *
    **/
add_action('init', 'custom_fix_thumbnail');

function custom_fix_thumbnail() {
    add_filter('woocommerce_placeholder_img_src', 'custom_woocommerce_placeholder_img_src');

    function custom_woocommerce_placeholder_img_src($src) {
        if (is_shop() || is_singular('product') || is_archive() || is_checkout() || is_cart()) {
            global $post;
            $array = get_the_terms($post->ID, 'product_cat');
            reset($array);
            $first_key = key($array);
            $thumbnail_id = get_woocommerce_term_meta($first_key, 'thumbnail_id', true);

            // get the image URL for parent category
            $image = wp_get_attachment_url($thumbnail_id);

            // print the IMG HTML for parent category
            if ($image)
                $src = $image;
        }
        return $src;
    }

}

There are some limitation for this code which i provided.
A product may have more than 1 categories assigned in this code i am using the image of the first category which i get.

Customize the if condition i.e. add and remove condition’s parameter according to your needs.