Image Savgol Filter (ENVI Classic)

The IMAGE_SAVGOL program applies the Savitzky-Golay smoothing filter to multispectral and hyperspectral images.  The filer is defined as a weighted moving average with weighting given as a polynomial of a certain degree.  The returned coefficients, when applied to a signal (spectrum in this case), perform a polynomial least-squares fit within the filter window. This polynomial is designed to preserve higher moments within the data and reduce the bias introduced by the filter. The filter can use any number of points for this weighted average andworks especially well when the typical peaks of the signal are narrow. The heights and widths of the curves are generally preserved.  For more information see the IDL help regarding the SAVGOL filter.

Place the image_savgol.sav in the \envixx\save_add directory of your ENVI installation.  A new button will appear under the Filter menu called 'Apply Savgol filter'.