I'm doing a form programmatically. I need to give an option to upload an image and give an option to resize it ( like cropping option ).

I don't know how to do it, I know that I need to upload the image to a directory and also I suppose that I need to show a relation between the node and the image in the database.

I've created a field called field_img.

So, how can I do it?

This is the form that I've done but I don't know how to give a relation in the database...

form['group_anuncio']['imagen'] = array(
        '#title' => t('Image'),
        '#type' => 'managed_file',
        '#upload_validators' => array('file_validate_extensions' => array('jpeg jpg png gif')),
        '#upload_location' => 'public://sites/default/files',
        '#progress_indicator' => 'throbber',
        '#status' => FILE_STATUS_PERMANENT,
        '#progress_message' => 'One moment while we save your file...',
);