How to programmatically generate pyramid files in ENVI Zoom

For large data files, ENVI Zoom builds pyramids in the background while loading the image into the display and prior to displaying the image in the Overview window.  Pyramids are copies of the data file at various reduced resolutions. They are used to speed image display by reducing the resampling required when displaying large portions of an image at low resolution.  ENVI Zoom only builds pyramids for a large data file the first time you open it. When you open the data file thereafter, it displays more quickly because it accesses the previously built pyramid file.  In some cases, it might be useful to build pyramid files programmatically and prior to accessing the data in Zoom.  The following code example shows how a pyramid file could be built programmatically:

    IDL> envizoom, /headless ; loads ENVI Zoom DLMs without the ENVI Zoom interface
    IDL> o = idlcfopenfile('e:\data\myfile.tif', /build_pyramid)

The above commands could be used in a loop to build pyramids for a directory of files thus reducing the time it takes to build pyramids on the fly.  However, it may be necessary to set the number of OPS's (out-of-process servers) in the ENVI Zoom preferences to 1 to avoid multiple pyramids from being built at once which could cause a strain on the system resources.  The OPS setting can be found in ENVI Zoom under File->Preferences->Application->OPS pool size.

Review on 12/31/2013 MM