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ENVI

Pyramids Background

Pyramids Background

ENVI builds pyramids for each image while loading the image into the display.

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. The Process Manager in the Status bar shows the progress of building pyramids when you open a data file. ENVI 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.

By default, pyramid files are created in the directory containing the original data file. If this directory is unavailable (due to write permission, for example), ENVI attempts to create the pyramid file in directory set in the Auxiliary File Directory preference. If this is not available, ENVI uses the IDL temporary directory. Files on network drives may be slower to build pyramids due to network issues.

Note: If your image has .ovr pyramid files, ENVI can use those.



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