generate documentation from config.sample.php

admin_manual/configuration_server/config_sample_php_parameters.rst

@@ -1946,7 +1946,13 @@ preview_imaginary_url
 
 Set the URL of the Imaginary service to send image previews to.
 
-Also requires the ``OC\Preview\Imaginary`` provider to be enabled.
+Also requires the
+ - ``OC\Preview\Imaginary``
+provider to be enabled in the 'enabledPreviewProviders' array, to create previews for these mimetypes:
+bmp, x-bitmap, png, jpeg, gif, heic, heif, svg+xml, tiff, webp and illustrator.
+If you want Imaginary to also create preview images from PDF Documents, you have to add
+ - ``OC\Preview\ImaginaryPDF``
+provider as well.
 
 See https://github.com/h2non/imaginary