[ptx] 16 bit and float image support in nona/hugin

[Pablo d'Angelo]

On Sun, 02 May 2004, Kai-Uwe Behrmann wrote:

> Am 02.05.04, 01:11 +0200 schrieb Pablo d'Angelo:
> 
> > I was wondering how an alpha channel look like in these format, and if
> 
> alpha:
> unsigned values - MIN -> Max  (0 .... 65535)
> signed values   - 0   -> MAX  (0 .... 32767)
> float/double    - 0.0 -> 1.0

Ok, I'll save the tiff files like that. Internally I'll use 8 bit alpha
channels.

> > somebody uses signed 16/32 bit images etc.
> 
> modern cameras, scanners, artists, scientists, hobbyists ;)

*g* The question was probably a bit unclear. I was thinking about who uses
signed 16 bit as opposed to unsigned 16 bit images.

> > Are there other popular formats for HDR images that should be
> > supported?

> Greg Wards old HDR format from radiance. And some more on
> <http://positron.cs.berkeley.edu/gwlarson/pixformat/index.html>
> 
> Sample implementations for:
> RGBE (hdr)
> OpenEXR
> TIFF (int8,int16,float,double,SGILogLuv)
> cineon
> in cinepaint <cinepaint.sf.net>, sources available
> 
> Basically RGBE/hdr and
> tiff (because You have allredy some code) are good starting points.

I'll stay with tiff and pnm (for reading dcraw output), at the beginning.
Unfortunately I had to modify vigra to be able to load unsigned tiffs
properly (impex always reports signed 16 / 32 bit images, even if they are
unsigned).

> All tags are definately needed, even so Compression Scheme and alpha can
> be adapted to ones needs.
> 
> The tiff stuff You should have allready, except of double reading
> and SGILogLuv, which is available on the patches site
> <http://sourceforge.net/tracker/index.php?func=detail&aid=834911&group_id=75029&atid=542708>.

Hmm, vigra doesn't support that I think. Is it in widespread use?

> Hope this helps

Yes, a good list of formats. Now I just have to fix some stuff and upload
the latest changes.

ciao
  Pablo