Work on modules/unsupported/coverageio is continuing.

As a complement to this page:

http://docs.codehaus.org/display/GEOTOOLS/Plugins+for+multidimensional+raster+data+sources

This is a few remarks:

* Current NetCDF reader (currently named DefaultReader, to be renamed as
  NetcdfReader later) expects a file following CF and COARDS conventions

  http://www.cfconventions.org/
  http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.html

  which expect for example axis in the (t,z,y,x) order. NetCDF File don't
  have to contain any of those axis, but if they do the convention ask to
  put them in that order. Some framework for plugin other conventions may
  be added in the future.


* Current NetCDF reader reads the third dimension (starting from the last
  one) as bands. This dimension is often 'z', but don't have to (the Reader
  don't know that it is z). The user don't have to read all bands from an
  image. I expect the user to select only one band using
  ImageReadParam.setSourceBands(int[]). In other words:

  - We already have ImageReadParam.setSourceRegion(Rectangle) for selecting
    a 2D subarea.
  - I use ImageReadParam.setSourceBands(int[]) as the way to make a selection
    in the third dimension using the standard Image I/O API.
  - The default ImageReadParam for NetcdfReader has band 0 pre-selected by
    default. So the user will not get all bands if he forget to select them.

  Note that NetCDF files don't have any notion of bands, just matrix. So we
  are not creating a conflict.


* The wiki page talk about a basic coverageio framework to be shared by
  plugins. The modules/unsupported/coverageio is an attempt for such basic
  framework, and coverageio-netcdf an experiment testing in the case of
  NetCDF file.


        Martin

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