[GRASS-user] Viewing ecw files

[Brad Douglas]

On Fri, 2007-02-16 at 12:03 +1300, Hamish wrote:
> > > Nicholas wrote:
> > > >> It would be really nice if GRASS had a wavelet based scheme for
> > > >> imagery, but that would require significant development and many
> > > >> of us don't have the spare time available.  At the moment,
> > > >> Hamish's suggestion is about the best that can be done.  GRASS
> > > >> cannot handle such large datasets with efficiency.
> > > >>
> > > >> ECW is a wonderful format.  It is hard to beat the compression
> > > >> and speed of scale change.
> Brad:
> > I did notice that there is an add-on r.wavelet module, but I have not
> > used it.  The backend library seems to be license-free and GPL, IIRC.
> > 
> > Wavelets for GRASS as an imagery format is "pie in the sky". :-\ 
> > There are too many other issues that need attention at the moment.
> 
> Hamish:
> maybe a r.external module could read/write GDAL formats (JPEG2000,
> ECW, MrSID..) as v.external does for OGR formats?
> 
> A simple script using gdal_translate to extract and import the current
> region (read-only) could be written in a few minutes. (r.in.gdal flag?)

The biggest problem is that when we import ECW in, it gets exploded to
very large sizes.  This is especially true for lossy compression where
ratios can reach > 50:1.

> FWIW, ER Mapper's ECW SDK page states "Free unlimited compression use in
> GPL style software".  http://www.ermapper.com/ProductView.aspx?t=28
> 
> Also that page claims that there is a lossless version available- which
> is a requirement for us. 

What they offer, we cannot use reliably as an internal format.  They
have competing products and we would be subject to their whim (they
reserve the right to modify the license as they see fit).  There are
some great people in the company who recognize the OSS community, but
there are also those who do not and are combative about the topic.

ECW complies with the JPEG2000 format, which is patented.  This is the
crux of the various JP2K codecs.  I don't know what current status of
the patent is.  Maybe it has been re-licensed to public domain or
similar or if there are cases that require a license.  Maybe someone can
research into that.  It does appear that there is some way around it.

I also think GeoJasPer[1] would be preferable to ECW, given our needs.
I'd much rather use a format that was built with OSS in mind, not as an
afterthought.

[1] http://www.dimin.net/software/geojasper/


-- 
Brad Douglas <rez touchofmadness com>                    KB8UYR/6
Address: 37.493,-121.924 / WGS84    National Map Corps #TNMC-3785