How to build an Imagefield like string in PHP

Question

I want to use Joomla's way to handle images in my component. My component offers a field to select a folder where some images are stored (used as gallery upon the related item). In dev everything works fine but on on staging the Website is currently available via domain.com/sub. The whole Joomla Installation is placed in this "sub" folder on the hosting environement. Now images in this gallery within my component are not working because of a wrong path on staging. But the images from the Joomla Media Field (item image) are working (the path there is correct interpreted by joomla itself - I think this is because of the way the image field stores the metadata and creates the image routes.

Is there a Helper class where i can insert the JPATH to an image and get the "joomla like" relativePath#joomlaImage://local-images/relativePath?width... out off?

I cand find anythin related in the Docs on how about create Image Metadata like the Image field does.

I think this could solve my path issues

Edit: Added Helper Class Code including quick and dirty fix

abstract class GalleryHelper {
    public static function getGalleryImages($type, $selectedFolder): array
    {

        $galleryImages = [];
        if($type === 'packages'){
            $folderToEquipmentImages = '/images/equipmentmanager/'.$type.'/galleries/';
        }else{
            $folderToEquipmentImages = '/images/equipmentmanager/'.$type.'/';
        }

        $imgsPath = JPATH_SITE . $folderToEquipmentImages . $selectedFolder;
        if (is_dir($imgsPath))
        {
            // Allowed filetypes
            $allowedExtensions = array('jpg', 'jpeg', 'png', 'gif');
            // Also allow filetypes in uppercase
            $allowedExtensions = array_merge($allowedExtensions, array_map('strtoupper', $allowedExtensions));
            // Build the filter. Will return something like: "jpg|jpeg|png|JPG|JPEG|PNG|gif|GIF"
            $filter = implode('|', $allowedExtensions);
            $filter = "^.*\.(" . implode('|', $allowedExtensions) . ")$";
            // Get the files
            $galleryImages = Folder::files($imgsPath, $filter, false, false, $exclude = array('index.html'));
            // Prepend the folder path to the filenames
            $galleryImages = array_map(function($img) use ($folderToEquipmentImages, $selectedFolder) {
                $folderToEquipmentImages = preg_replace('#/#', '', $folderToEquipmentImages, 1);
                return  \JUri::base() . $folderToEquipmentImages . $selectedFolder . '/' . $img;
            }, $galleryImages);

        }
        return $galleryImages;
    }
}

As you can see i had to use the slash at the beginning to find the images in the filestystem and then remove it later in the foreach loop to generate the full URI