Changes in pixmap version 0.3-0

  o The whole package has moved to S4 classes and methods, hence all
    classes have a new representation. This also means that the code
    and the API are not fully backwards compatible with earlier
    versions of the package. 

  o Added support for subsetting (see example(pixmap)).

  o New: addChannels() and getChannels().


Changes in pixmap version 0.2-1

  o pixmap():
    - Added arguments bbcent and cellres
    - nrow and ncol default to the respective dimensions of the data
      argument (if present). Hence, pixmap does the expected when
      given a matrix or an array.
    - data is rescaled to [0,1] for rgb and grey, and coerced to positive
      integers for indexed.   
    - col can also be a function like rainbow()

Changes in pixmap version 0.1-2

  o Fixed bugs in plotting, read.pnm and write.pnm which confused
    dimensions (rows versus columns), but together let plots look OK.

