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Subject: [Tiff] TIFF support for 16 bit floats
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On 02/14/2013 10:00 AM, tiff-request@lists.maptools.org wrote:
>     4. Re: 32 bit to 16bit conversion (Bob Friesenhahn)
>
>
>
> Message: 4
> Date: Thu, 14 Feb 2013 09:08:33 -0600 (CST)
> From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
> Subject: Re: [Tiff] 32 bit to 16bit conversion
> To: james wells <jwneuror@gmail.com>
> Cc: "tiff@lists.maptools.org" <tiff@lists.maptools.org>
> Message-ID:
> 	<alpine.GSO.2.01.1302140905120.11141@freddy.simplesystems.org>
> Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
>
> On Thu, 14 Feb 2013, james wells wrote:
>
>> It's a 32 bit float, a hightmap, and I need to convert it to a 16 bit float, so hopefully it's not as painful?
>>
>> I'll take a look at ILM's half library when I get home, looks interesting, hopefully not too out of my league.
> There are also C-language implementations of 16-bit 'Half' in
> GraphicsMagick and in littlecms (lcms).  Both of these are offered
> under a liberal (MIT/X11) license.
>
> OpenEXR is quite large and primarily written in C++ so using it just
> for Half support would be painful.
>
> Bob
I'd be interesting in seeing a sample of the data.  I have C routines to
convert between 16, 24, and 32 bit floats that I'm hoping to update in
the not-to-distant future and I'd like to compare results with my
routines to whatever else you might find out there.  I can also share
them in their present form if you are interested.  Bob can comment on
the differences between the implementations.  The ones in lcms are table
based whereas mine are iterative.  I have options to round out of domain
values to the maximum supported by the desired bit depth or to treat
them as errors.  My plan is to eventually add these routines to tiffcrop
so that you could use tiffcrop to do this for you in one step.

Richard Nolde



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