Declaration: TMetaData.PurifyPixAttrib;
The method PurifyPixAttrib shifts used pixel attributes down towards attribute zero. After the purification all used N attributes are populating the first N attribute numbers (0 to N-1), all unused attributes are cleared (i.e. the names of unused attributes are deteled). This method always effects all attribute layers.

Hint: In order to directly access the metadata of the currently loaded dataset you can use the pre-declared global variable MData.