This is the Dtk_Preview class.
A Dtk_Preview is a Thumbnail image that may exist in a CAD file.
A Dtk_Preview contains Stream representing picture data This class lets you use Dtk_Preview.
You can get a preview for a Dtk_Component and/or Dtk_Node.
Using GetPreview() method of Dtk_Component retrieves the model preview.
Using GetPreview() method of Dtk_Node retrieves the node preview (for example a drawing type node).