Example snippet to prepend and append image generators for The SEO Framework.

tsf-custom-image-generator.php

<?php
// Do not include this PHP opening tag if PHP is already opened...
// Ref: https://theseoframework.com/docs/using-filters/


add_filter( 'the_seo_framework_image_generation_params', 'my_tsf_custom_image_generation_args', 10, 3 );
/**
 * Adjusts image generation parameters.
 *
 * @link https://theseoframework.com/docs/api/filters/#append-image-generators-for-social-images

 * @param array      $params : [
 *    string  size:     The image size to use.
 *    boolean multi:    Whether to allow multiple images to be returned.
 *    array   cbs:      The callbacks to parse. Ideally be generators, so we can halt remotely.
 *    array   fallback: The callbacks to parse. Ideally be generators, so we can halt remotely.
 * ];
 * @param array|null $args The query arguments. Contains 'id' and 'taxonomy'.
 *                         Is null when query is autodetermined.
 * @return array $params
 */
function my_tsf_custom_image_generation_args( $params = [], $args = null, $context = 'social' ) {

	// Let's not mess with non-social sharing images.
	if ( 'social' !== $context )
		return $params;

	if ( null === $args ) {
		// In the loop.
		if ( is_singular() ) {
			$params['cbs'] = array_merge(
				[ 'custom' => 'my_custom_tsf_singular_image_generator' ],     // prepend to regular callbacks.
				$params['cbs'],
				[ 'other' => 'my_other_tsf_custom_singular_image_generator' ] // append to regular callbacks.
			);
		}
	} else {
		// Out the loop. Use $args to evaluate the query...
		if ( ! $args['taxonomy'] ) {
			// Singular.

			$params['cbs'] = array_merge(
				[ 'custom' => 'my_custom_tsf_singular_image_generator' ],     // prepend to regular callbacks.
				$params['cbs'],
				[ 'other' => 'my_other_tsf_custom_singular_image_generator' ] // append to regular callbacks.
			);
		}
	}

	return $params;
}

/**
 * Generates image URL and ID via my_get_image_value.
 *
 * @generator
 *
 * @param array|null $args The query arguments. Accepts 'id' and 'taxonomy'.
 *                         Leave null to autodetermine query.
 * @param string     $size The size of the image to get.
 * @yield array : {
 *    string url: The image URL location,
 *    int    id:  The image ID,
 * }
 */
function my_custom_tsf_singular_image_generator( $args = null, $size = 'full' ) {

	// Obtain the post ID... (unused in this example)
	$post_id = isset( $args['id'] ) ? $args['id'] : the_seo_framework()->get_the_real_ID();

	// Get the image...
	$image_params = [
		'url' => 'https://example.com/path/to/image.jpg',
		'id'  => 42, // Optional..
	];

	// Feel free to loop this. Ref: `The_SEO_Framework\Builders\Images::get_content_image_details()`
	if ( ! empty( $image_params['url'] ) ) {
		yield [
			'url' => $image_params['url'],
			'id'  => isset( $image_params['id'] ) ? $image_params['id'] : 0,  // Optional. Used for alt-tag and dimension fetching.
		];
	} else {
		// Since we don't support PHP 7.0+ only yet in TSF, we must trigger the generator here on failure ("yield from" is unavailable).
		yield [
			'url' => '',
			'id'  => 0,
		];
	}
}

// Refer to my_tsf_custom_singular_image_generator()
function my_other_tsf_custom_singular_image_generator( $args = null, $size = 'full' ) { }