Main Window - Edit | Copy | Image                    Ctrl+C

Thumbnail Popup Menu - Clipboard | Copy Image

 

 

This option copies the first selected file to the clipboard in the appropriate format for the file for raster images or metafile for vector images). If no files are selected, this menu option is disabled.

 

You can make this option the default (double-click) option from the main menu selection Options | Preferences - General.