设置后缩略图大小wordpress - 百分比

I am trying to generate all my uploaded images sizes by either

set_post_thumbnail_size( $width, $height, $crop );

or add custom size

add_image_size()

but the problem is: I dont want fixed width or height I want to set it to percentage like half 50% something like this:

set_post_thumbnail_size( 50%, 50%, $crop ); set_post_thumbnail_size( 50%, auto, $crop );

Try this:

if(has_post_thumbnail()) {                    
    $image_src = wp_get_attachment_image_src( get_post_thumbnail_id(),'full' );
     echo '<img src="' . $image_src[0]  . '" width="100%"  />';
}