In D551#11308, @erik wrote:

\ImageHelper::ResizeImage - change "thumb_format" of poll's "Image" field to "resize:200x200;default:core/admin_templates/img/ajax_iframe_progress.gif" and try uploading a large (>200 by width/height) file on the poll editing page in the Admin Console

convertPathToRelative is called to convert each element in the $params array, however only "default" parameter contains file path. There are made excessive convertPathToRelative calls for some parameters (quality, output_format, etc.)