how to add_filter to function ?

Hello guys

the idea is apply some filters if the user select the option in the theme, but i have a problem

i made a function that replace the post_thumbnail_html for a personalized html

then, i create other function that create thumnails for timthumb

i’m trying to apply the add_filter to the timthumb function, but it doesn’t work

can you helpme?

function kandombe_theme_thumb($id, $width, $height, $align='') {

		//some code

		$html = '<img class="archive_thumb" src='.$image_url.' width="'.$width.'" height="'.$height.'"/>';

		return $html;

	}

if ($data['speed_lazy_loading']) { 

	function kandombe_lazy_loads( $html ) {

		//some code

		$html = preg_replace( '#<img([^>]+?)src=[\'"]?([^\'"\s>]+)[\'"]?([^>]*)>#', sprintf( '<img${1}src="%s" data-original="${2}"${3} style="display: block;"><noscript><img${1}src="${2}"${3}></noscript>', $placeholder_image ), $html );

	return $html;
	}

add_filter( 'the_content', 'kandombe_lazy_loads');
add_filter( 'post_thumbnail_html', 'kandombe_lazy_loads');
add_filter( 'kandombe_theme_thumb', 'kandombe_lazy_loads');
add_filter( 'get_avatar', 'kandombe_lazy_loads');

}