Changes between Version 15 and Version 16 of rfc15_nodatabitmask

Timestamp:

Dec 19, 2016, 4:36:43 AM (7 years ago)

Author:

Even Rouault

Comment:

Give details about expectations for .msk files

rfc15_nodatabitmask

@@ -50 +50 @@
 The GDALRasterBand will include a protected poMask instance variable and a bOwnMask flag.  The first call to the default !GetMaskBand() will result in creation of the GDALNodataMaskRasterBand, GDALAllValidMaskRasterBand and their assignment to poMask with bOwnMask set TRUE.  If an alpha band is identified for use, it will be assigned to poMask and bOwnMask set to FALSE.  The GDALRasterBand class will take care of deleting the poMask if set and bOwnMask is true in the destructor.  Derived band classes may safely use the poMask and bOwnMask flag similarly as long as the semantics are maintained.
 
+For an external .msk file to be recognized by GDAL, it must be a valid GDAL
+dataset, with the same name as the main dataset and suffixed with .msk,
+with either one band (in the GMF_PER_DATASET case), or as many bands as the
+main dataset.
+It must have INTERNAL_MASK_FLAGS_xx metadata items set at the dataset
+level, where xx matches the band number of a band of the main dataset. The
+value of those items is a combination of the flags GMF_ALL_VALID,
+GMF_PER_DATASET, GMF_ALPHA and GMF_NODATA. If a metadata item is missing for
+a band, then the other rules explained above will be used to generate a
+on-the-fly mask band.
+
 == Default !CreateMaskBand() ==