[CREATE] Requirements on PNG data in OpenRaster files

[Andrew Chadwick]

It would be a good idea to place some limitations and requirements on
PNG file data in OpenRaster files.

Proposal:
http://www.freedesktop.org/wiki/Specifications/OpenRaster/Draft/PngDataRequirements

Could interested parties on this list please read the proposal and
comment on the text here? Thanks.


Quick summary:

* Recommend the PNG format for layer data. It's a good format for flat
raster graphics, and permitting any format for use in layers will be
problematic. Should I leave more room open for things like SVG layers?

* State that CM information should be written to PNGs inside ORA
files, and read/used when loading them (without placing any
requirements on pixel storage inside apps)

* Advise writers to not use interlacing (it's not like ORA is a
streaming format).

* Thumbnails should be sRGB for greater compatibility with desktop
thumbnail management software.

-- 
Andrew Chadwick