View source  
  <?php
namespace Drupal\image\Plugin\ImageEffect;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Image\ImageInterface;
class CropImageEffect extends ResizeImageEffect {
  
  public function applyEffect(ImageInterface $image) {
    list($x, $y) = explode('-', $this->configuration['anchor']);
    $x = image_filter_keyword($x, $image
      ->getWidth(), $this->configuration['width']);
    $y = image_filter_keyword($y, $image
      ->getHeight(), $this->configuration['height']);
    if (!$image
      ->crop($x, $y, $this->configuration['width'], $this->configuration['height'])) {
      $this->logger
        ->error('Image crop failed using the %toolkit toolkit on %path (%mimetype, %dimensions)', array(
        '%toolkit' => $image
          ->getToolkitId(),
        '%path' => $image
          ->getSource(),
        '%mimetype' => $image
          ->getMimeType(),
        '%dimensions' => $image
          ->getWidth() . 'x' . $image
          ->getHeight(),
      ));
      return FALSE;
    }
    return TRUE;
  }
  
  public function getSummary() {
    $summary = array(
      '#theme' => 'image_crop_summary',
      '#data' => $this->configuration,
    );
    $summary += parent::getSummary();
    return $summary;
  }
  
  public function defaultConfiguration() {
    return parent::defaultConfiguration() + array(
      'anchor' => 'center-center',
    );
  }
  
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    $form = parent::buildConfigurationForm($form, $form_state);
    $form['anchor'] = array(
      '#type' => 'radios',
      '#title' => t('Anchor'),
      '#options' => array(
        'left-top' => t('Top left'),
        'center-top' => t('Top center'),
        'right-top' => t('Top right'),
        'left-center' => t('Center left'),
        'center-center' => t('Center'),
        'right-center' => t('Center right'),
        'left-bottom' => t('Bottom left'),
        'center-bottom' => t('Bottom center'),
        'right-bottom' => t('Bottom right'),
      ),
      '#theme' => 'image_anchor',
      '#default_value' => $this->configuration['anchor'],
      '#description' => t('The part of the image that will be retained during the crop.'),
    );
    return $form;
  }
  
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
    parent::submitConfigurationForm($form, $form_state);
    $this->configuration['anchor'] = $form_state
      ->getValue('anchor');
  }
}