’s logical quality masking flag. This flag determines whether the NDF
’s quality component (if present) will be used to generate
"pixel values for automatic insertion into the data and variance arrays when these are accessed in READ or UPDATE mode. Normally, this automatic quality masking is used to convert quality information into
"pixels so that an application need not consider the quality information explicitly. If the quality masking flag is set to .FALSE., then automatic masking will not occur so that the application can process the quality component by accessing it directly.
A quality masking flag is associated with each NDF identifier and is initially set to .TRUE.. Its value changes to .FALSE. whenever the quality component is accessed directly (e.g. using NDF_MAP or NDF_MAPQL) and reverts to .TRUE. when access is relinquished (e.g. using NDF_UNMAP). This default behaviour may also be over-ridden by calling NDF_SQMF to set its value explicitly. NDF_QMF allows the current value to be determined.