ENVI Classic: Save Interpolated Image Displayed in Zoom Window

There are times when ENVI users would like to be able to save the Zoom window image with one of the interpolation methods applied. Currently, there is no interactive way to do this. When the zoom image is saved via File -> Save Zoom As -> Image File, only the standard (non-interpolated) zoom image is saved. This Tech Tip will outline workaround methods to achieve the desired results.

The first workaround for customers on the Windows platform involves just creating a screen capture of the window and pasting it into another document. This is somewhat cumbersome, at best, and doesn't work for UNIX users.

The second solution is more elegant and functional. The user function called "save_zoom_to _generic_formats.pro" will accomplish this by allowing outputs in the following formats: TIFF, BMP, JPEG and PNG. The code for this user function is available from the Exelis VIS User-Contributed Library:

http://www.exelisvis.com/UserCommunity/CodeLibrary.aspx

This program uses the IDL routine "TVRD" to grab a screenshot of the display area for the selected ENVI Zoom window *exactly* as it currently appears. Most of the time this results in a What-You-See-Is-What-You-Get image output to the selected generic format image file. Consequently, any overlays, zoom graphics, crosshairs, annotations, etc. currently visible within the Zoom window will be output to the image file on disk. For example, the Zoom window graphics boxes in the lower-left hand corner will be output in their current color unless you turn them off by right-clicking within the Zoom window and from the context menu select "Toggle > Zoom Graphics Off". Furthermore, there can be problems using TVRD when backing store is provided by the window system (from the ENVI main menu "File > Preferences > Display Defaults > Display Retain Value" is set to 1). Having ENVI provide the backing store (set Display Retain Value to 2) ensures that the window contents will be read properly. In addition, there can be issues reading from an iconified or hidden window on X Windows display devices. For more information consult the "Unexpected Results Using TVRD with X Windows" section of the Reference Guide entry for the TVRD routine in the IDL documentation.

Usage:
This program must be called directly from an interactive session of ENVI as an"ENVI User Function". The most logical way to add this program to an ENVI installation is by editing the "display.men" ASCII text file, in the menu directory under the ENVI installation, and inserting a menu selection item line in the following manner:

1 {Save Zoom As}

2 {Image File...} {output zoom} {disp_event}
2 {Generic Format...} {} {save_zoom_to_generic_formats} *** add this line