Here is another example, make sure you rename the function

function my_custom_function_name( ){
global $imstore,
remove_filter( 'wp_update_attachment_metadata', array($imstore, 'generate_image_metadata'));
remove_filter( 'wp_generate_attachment_metadata', array($imstore, 'generate_image_metadata'));
}
add_action( 'ims_admin_init',  'my_custom_function_name', 100 );