Change History (7)
comment:1 by , 15 years ago
Milestone: | → 1.6.1 |
---|---|
Version: | unspecified → 1.6.0 |
comment:2 by , 15 years ago
Keywords: | overview added |
---|---|
Owner: | changed from | to
Gao,
Are you suggesting that the overview raster bands should return a properly set nodata value when GetNoDataValue() is called on the overview band object?
In general GDAL has taken the approach that applications should not depend on metadata such as color tables, nodata, RATs, and so forth existing on overviews, though in some cases they might. So, my preliminary thought is that the application should be careful to use the full resolution band for all metadata.
comment:3 by , 15 years ago
In my test case, GetMaskFlags() returns GMF ALL_VALID on the overview band object, and the actually pixel value in the overviews for the NoData area is not the NoData value returned from the base raster band. It's will be nice the flag indicates there are NoData pixels in the overviews. The pixel value for NoData area in the overview band should match the NoData value.
comment:4 by , 15 years ago
Status: | new → assigned |
---|
I have confirmed that nodata/mask information is propagated to .ovr style overviews but not to imagine format overviews (ie. rrd or built-in to .img overviews). I will correct this.
comment:5 by , 15 years ago
Keywords: | HFA added |
---|---|
Milestone: | 1.6.4 |
Gao,
I believe this has been corrected now in trunk (r18625), 1.7 (r18626) and 1.6-esri (r18627).
The solution was to ensure nodata values were propagated into the .img during CreateCopy() (not just to the aux.xml file) and then to ensure they were carried into the overview in hfaopen.cpp:CreateOverview().
comment:6 by , 15 years ago
Resolution: | → fixed |
---|---|
Status: | assigned → closed |
I have extended the trunk autotest suite with verification of this new feature (r18628).
Addition information:
BuildOverviews generated two large file, an .ige (2,581,940K) and a .rrd file (865,082K). If I force it to generate ovr type of overviews (removing the .aux), the generated .ovr file is only 101,884K bytes.