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Date: Tue, 09 Sep 2008 17:06:27 -0700
Subject: Re: [Tiff] SAMPLEFORMAT_IEEEFP
From: Chris Cox <ccox@adobe.com>
To: acanicio <acanicio@astrosnap.com>, TIFF <tiff@lists.maptools.org>
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Thread-Topic: [Tiff] SAMPLEFORMAT_IEEEFP
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They don't have to be between zero and one - but that is the default viewing
range.
There are adjustments to change the value ranges, and a viewing exposure
slider to change the viewing exposure.

I mean use the adjustment named Exposure in Photoshop to scale the data.
If that works, then you can scale it when doing your conversion.

Chris



On 9/9/08 12:02 AM, "acanicio" <acanicio@astrosnap.com> wrote:

> 
> Dear Bruce and Chris,
> 
> Thank you !
> I didn't know that floating point values had to be between 0 and 1 !!
> When converting to float, I kept the original range, i.e. 0..255 when coming
> from 8 bits, 0..65535 when coming from 16 bits, and 0..4294967295.
> 
> What do you mean by "Use the exposure adjustment " ? Is there some specific
> tag for this or is it the same thing as scaling down ?. I see tag
> TIFFTAG_REFERENCEBLACKWHITE in the specifications. Is that it ?
> 
> I'll try as you say, thank you very much to both of you.
> 
> Best regards
> Axel
> 
> 
> 
> 
> Chris Cox wrote:
>> 
>> 
>> Use the exposure adjustment and scale the values down.
>> 
>> Most of the time, you should scale your white point to something near 1.0
>> to
>> ensure visibility.
>> 
>> Chris
>> 
>> 
>> 
>> 
>> 
>> On 9/7/08 4:18 PM, "acanicio" <acanicio@astrosnap.com> wrote:
>> 
>>> But I have no luck with floating point values. I use SAMPLEFORMAT_IEEEFP
>>> sample format along with 32 bits per sample.
>>> All the pixel values are issued from an 8 bit/sample image, with no
>>> conversion or multiplication applied to them.
>>> When I open the file with some well known image editor, the image is
>>> completely saturated, all white with values 32767...
>>> Where should I look ?
>> 
>> _______________________________________________
>> Tiff mailing list: Tiff@lists.maptools.org
>> http://lists.maptools.org/mailman/listinfo/tiff
>> http://www.remotesensing.org/libtiff/
>> 
>> 

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