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add_filter( 'woocommerce_get_image_size_single', 'custom_wc_product_img_size' );
add_filter( 'woocommerce_get_image_size_shop_single', 'custom_wc_product_img_size' );
add_filter( 'woocommerce_get_image_size_woocommerce_single', 'custom_wc_product_img_size' );
function custom_wc_product_img_size() {
	$size = array(
		'width'  => 800,
		'height' => 800,
		'crop'   => 1,
		);

		return $size;
}