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Saving and Restoring ENVI Sessions

Barrett Sather

I've been using the latest release of ENVI for a while now, and have gotten used to the new bells and whistles. My favorite though, is the ability to save your work! Now, if I can't finish a project in one sitting, I can save the current session, and restore it later.

The mechanics of the save are quite simple; ENVI stores all of the open layers, files, ROIs, vectors, etc... in a text file in Javascript Object Notation Format (or JSON). All of the properties of layers like bands loaded, brightness, and transparency are all saved as well. This way, when you restore a previous session, ENVI knows the steps to take to get back to the state you were in during the save. I like it. Elegant, and simple. To get more info on how to use Save / Restore session head to the page in our documentation center.

A couple things to remember when using this save mechanism:

  • ENVI only restores files and any properties like stretch, and bands. If you make changes to a shapefile or ROI, it is best to save those files as well as ENVI's state in order to get back the expected layers and files. In other words, Save Everything!
  • This method makes it so that your save files arevery small, since it is only text. Because of this, ENVI will have to restore all of the file connections and reload them to the display. It's a trade off - smaller save file means a longer restore time.
  • Not just raster layers are saved - even display tools like annotations and portals can be restored from the JSON save file.

Here's an example of an ENVI session that will be fully restored by saving, quitting the application, then resorting the session:

  

So what gets restored for this particular example?        

  1.         The two raster files in the display with the same band combination and properties.
  2. The Region of Interest over the building.
  3.         The text annotation "SAVE ALL".
  4.         The portal, and portal location.
  5.         The positioning - ie. the zoom level, center of the screen, and rotation.

 

This is a simpler example of what this tool can do, as I set this view up in just a few minutes. If you've been working for an hour though, and want to save your work for after lunch, or even till Monday, this is a safe way to do it without taking up much disk space.

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