Get diagram picture from DM with OSLC

The recommended way is to use the OSLC specifications to get the Diagram preview which includes in the expanded form the diagram image.
The URI will be something like this:
https://localhost:9443/dm/_ajax-modules/rmps.web.app.ResourceLinkViewer?resourceUri=https%3A%2F%2Flocalhost%3A9443%2Fdm%2Fmodels%2F_qQ9Bwgp8EeWGMPdW6ZQc2w~GUID__613d0d38-d350-4ad4-9720-0ef268204eec&isExpanded=true&projectArea=Rhapsody%20Sample%20Project&rmps.context=https%3A%2F%2Flocalhost%3A9443%2Fdm%2Fstreams%2F10

If you want the image only, you can use the following API (internal, subject to change):
https://<localhost>:9443/dm/diagrams/image?diagramUri=<encoded diagram uri>&rmps.context=<encoded context uri>
ex.
https://localhost:9443/dm/diagrams/image?diagramUri=https%3A%2F%2Flocalhost%3A9443%2Fdm%2Fmodels%2F_qQ9Bwgp8EeWGMPdW6ZQc2w~GUID__613d0d38-d350-4ad4-9720-0ef268204eec&rmps.context=https%3A%2F%2Flocalhost%3A9443%2Fdm%2Fstreams%2F10