ISIS Documentation

gradient

Apply Sobel or Roberts gradient to a cube

This program will apply a Sobel or Roberts gradient filter to a cube. These gradient filters will highlight edges of an image. Gradient filters typically are used to highlight the differences in the brightness of adjacent pixels in a cube, and also the edges of the transitions in the image data. The output will contain the calculated magnitude of the spatial graident of the input cube. The calculation method can be set to either exact or approximate and can be specified with the 'METHOD' parameter. NOTE: When a calculation must be done where one or more values are special pixels, the output will be NULL. If this causes unexpected results, you can run stretch to change ithe input special pixel(s) to a Digital Number (DN) that is appropriate for calculation. For example, if the image contains High Instrument Saturation (HIS) values, you may choose to stretch these to 255 prior to running the gradient filter.

Categories


History

Tracie Sucharski2002-12-18 Original version
Kim Sides2003-05-13 Added application test
Stuart Sides2003-05-16 Modified schema location from astogeology... to isis.astrogeology..."
Stuart Sides2003-07-29 Modified filename parameters to be cube parameters where necessary
Drew Davidson2005-08-16 Added examples
Brendan George2005-11-07 Modified to handle Special Pixels
Ian Humphrey2015-05-18 Added METHOD parameter to allow for either exact or approximate calculation of the gradient magnitude. Updated and added tests. Updated documentation. Fixes #1741.