[magick-users] J2K (JPEG 2000 codestream) support

[duc.sequere.aut.de.via.decede at imagemagick.org]

> As a side note pnm seems to be working.

We got an error with the PNM format as well:

  jasper --input D_CLUNIE_CT1_J2KI.j2k --output test.pnm
  warning: support for signed sample data requires use of nonstandard
    extension to PNM format
  You may not be able to read or correctly display the resulting PNM data with
    other software.

However, we'll look into normalizing the data in the case where ImageMagick
does not have the HDRI option set.