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//add category class to img tag when adding media

function give_linked_images_class($html, $id, $caption, $title, $align, $url, $size, $alt = '' ){
	$classes = '';
	if (has_term('','att_tax',$id)) {
		$terms = wp_get_post_terms($id, 'att_tax');
		if ($terms) {
			foreach ($terms as $term) {
				$classes .= $term->slug.' '; // separated by spaces, e.g. 'img image-link'
			}
		}
	}

	// check if there are already classes assigned to the anchor
	if ( preg_match('/<a.*? class=".*?">/', $html) ) {
	$html = preg_replace('/(<a.*? class=".*?)(".*?>)/', '$1 ' . $classes . '$2', $html);
	} else {
		$html = preg_replace('/(<a.*?)>/', '$1 class="' . $classes . '" >', $html);
	}
	return $html;
}
add_filter('image_send_to_editor','give_linked_images_class',10,8);