Package allows to modify image's metadata.
You have to install modExif dependencies via Composer after successful installation at MODX Package Manager. ModExif uses pThumb for thumb generation. That's why pThumb should be installed too;
<?php
$path = MODX_CORE_PATH . 'components/modexif/model/';
$modx->getService('exif', 'modExif.modExif', $path);
$image = $modx->runSnippet('exifthumb', array(
'input' => $imageUrl,
'options' => array(),
'exif' => '[{"name":"Nickname","value":"proxyfabio"}]'
));
$path = MODX_CORE_PATH . 'components/modexif/model/';
$modx->getService('exif', 'modExif.modExif', $path);
$metadata = $modx->exif->exifRead($image);