How to throw admin notice error on image upload

Question

I created a plugin that creates a new image size and turns it B&W.

I need the script to throw an notice if the user upload an image smaller then 1000x1000.

I tried this, but Wordpress is ignoring it, it just gives me a general HTTP error.

GENERATE IMAGE SIZE

function register_watermarked_size() {

  add_image_size( 'watermarked', 1000, 1000 ); 
}
add_action( 'init', 'register_watermarked_size' ); 

GENERATE IMAGE Here I check the image size.

function generate_watermarked_image( $meta ) {

  if ( $meta['width'] < 1000 && $meta['height'] < 1000 ) {
    add_action( 'admin_notices', array( $this, 'watermark_error') );
  }
  else {    
    // do some stuff...
    return $meta;
  }
}
add_filter( 'wp_generate_attachment_metadata', 'generate_watermarked_image' );

ERROR MESSAGE METHOD

function watermark_error() {

    $class = 'notice notice-error';
    $message = "Sorry, this image cannot be uploaded. \nEach side must be longer than 1000px.";
    printf( '<div class="%1$s"><p>%2$s</p></div>', $class, $message ); 
}