ImageCacheActions.php

<?php

namespace Drupal\image\Plugin\migrate\process\d6;

use Drupal\migrate\MigrateExecutableInterface;
use Drupal\migrate\ProcessPluginBase;
use Drupal\migrate\Row;

/**
 * @MigrateProcessPlugin(
 *   id = "d6_imagecache_actions"
 * )
 */
class ImageCacheActions extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        $effects = [];
        foreach ($row->getSourceProperty('actions') as $action) {
            if (empty($action['action'])) {
                continue;
            }
            $id = preg_replace('/^imagecache/', 'image', $action['action']);
            if ($id === 'image_crop') {
                $action['data']['anchor'] = $action['data']['xoffset'] . '-' . $action['data']['yoffset'];
                if (!preg_match('/^[a-z]*\\-[a-z]*/', $action['data']['anchor'])) {
                    $migrate_executable->message
                        ->display('The Drupal 8 image crop effect does not support numeric values for x and y offsets. Use keywords to set crop effect offsets instead.', 'error');
                }
                unset($action['data']['xoffset']);
                unset($action['data']['yoffset']);
            }
            $effects[] = [
                'id' => $id,
                'weight' => $action['weight'],
                'data' => $action['data'],
            ];
        }
        return $effects;
    }

}