Uploading images to custom Widgets

[Brew Digital]

I'm in the process of creating some custom widgets. I'd like to be able to upload images to the widget.

So far I've managed to get an image upload working that creates a smaller thumbnail to be used by the widget. 

The problem I have is that I can't figure out how to remove the previously uploaded image before replacing it with a newly uploaded one.

Below is what I have so far, any advice on how to handle this would be much appreciated. 

/**
 * notification Widget
 */
class _notification extends \IPS\Widget\StaticCache
{
    /**
     * @brief    Widget Key
     */
    public $key = 'notification';

    /**
     * @brief    App
     */
    public $app = 'pslwidget';

    /**
     * @brief    Plugin
     */
    public $plugin = '';

    /**
     * Initialise this widget
     *
     * @return void
     */
    public function init()
    {
        parent::init();
    }

    /**
     * Specify widget configuration
     *
     * @param null|\IPS\Helpers\Form $form Form object
     * @return    null|\IPS\Helpers\Form
     */
    public function configuration(&$form = null)
    {
        /** @var _Form $form */
        $form = parent::configuration($form);
        $form->add(new \IPS\Helpers\Form\Upload(
            'widget_field',
            isset($this->configuration['widget_field'])
                ? \IPS\File::get('core_Application', $this->configuration['widget_field']['url']['path'])
                : null, true,
            ['storageExtension' => 'core_Application']));
        $form->add(new \IPS\Helpers\Form\Text('title',
            isset($this->configuration['title'])
                ? $this->configuration['title']
                : ''
        ));

        return $form;
    }

    /**
     * Ran before saving widget configuration
     *
     * @param array $values Values from form
     * @return    array
     */
    public function preConfig($values)
    {
        if (isset($values['widget_field'])) {
            /** @var _File $temp */
            $temp = $values['widget_field'];
            $values['widget_field'] = $temp->thumbnail('core_Application', 400);
            $temp->delete();
        }

        return $values;
    }

    /**
     * Render a widget
     *
     * @return    string
     */
    public function render()
    {
        $title = isset($this->configuration['title']) ? $this->configuration['title'] : null;
        $image = isset($this->configuration['widget_field']) ? $this->configuration['widget_field'] : null;
        if (!$image) {
            return $this->output($title, '#');
        }

        return $this->output($title, $image["url"]["data"]["path"]);
    }
}