Have you experianced 'customized' Widget, which is used to Export /Clip a 'georeferanced' image (change image) in Web App from ArcGIS Online / Portal for ArcGIS?
The widget of 'Export' should be similar to one that is used in desktop ArcGIS... (i.e., georeferanced image, rather than 'snapshot'). Of course, the image service in Web App (ArcGIS Online /Portal for ArcGIS) is 'exportable', which is configured at GIS server-side.
Can you share any hands-on or thoughts?