Mickaël, > > > >> * The size of the overview at level 'n' is computed as : ovr_size = > >> raster_size / 2^n , whereas it should be ovr_size = ceil( > >> raster_size / float(2^n) ) > >> > > > > Hum, any reason to particularly round to the upper value rather than > > the lower > > value ? The JP2ECW driver does the rounding to the lower value too. > > The upper method is defined by the JPEG2000 norm (Annex B of the Part1)
ok, and that's what openjpeg use too ? If so, we might have inconsistencies between the expectations of the GDAL driver when it calls openjpeg API and the dimensions reported by openjpeg. That might actually remind me of something I saw at the time where the driver was developed. > > > > >> > >> I am using GDAL 1.10.1 and OpenJpeg 2.0. > >> Is it relevant to report a bug on this topic ? > > > > IMHO the test case seems to be a bit too artificial to justify any change, > > unless there are real world cases where that would cause issues. > > > Yes it is not a real case but it is a conformance data which allow to > define if a decoder is JPEG decoding compliant. It helps to verify > that real less complicated case will be handled properly. For example > we can see that JP2ECW is not compliant about this point. Yeah, but ultra pedantry compliance testing can lead to less performance or other issues in real world cases so there's a trade-off to evaluate. The JP2ECW driver is used happily in production even if it isn't strictly compliant on that point. Anyway if you want to provide a well tested patch for the issue related to overview dimensions, please do so. As far as reporting overview levels whose dimension is < 256, there's a risk of consumming more file descriptors than reasonable (see http://lists.osgeo.org/pipermail/gdal-dev/2014-May/039155.html). Unless you want to restructure the driver a bit so that all overviews share the same file descriptor. But I guess some saving/restoring of the position would have to be implemented, so that you can switch arbitrarily between overviews. I remember some headaches with openjpeg since it has a tendancy of segfaulting if you don't reset it properly between requests of blocks made in random order, so I prefered to assign a file descriptor to each overview level. Best regards, Even _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
