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Date: Fri, 06 Apr 2007 11:41:50 -0700
Subject: Re: [Tiff] Floating point RGBA
From: Chris Cox <ccox@adobe.com>
To: Toby Thain <toby@smartgames.ca>
Message-ID: <C23BE27E.52011%ccox@adobe.com>
Thread-Topic: [Tiff] Floating point RGBA
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Status:   

LZW will expand floating point data, as it frequently does with 16 bit da=
ta.

ZIP does a decent job with straight floating point values.

But to get good compression, you need a predictor that knows about the
floating point format.  (and I'm still researching better ones)

Chris



On 4/5/07 1:04 PM, "Toby Thain" <toby@smartgames.ca> wrote:

>=20
> On 5-Apr-07, at 4:58 PM, Craig Bruce wrote:
>=20
>> "Joris" <joris.at.lebbeke@skynet.be> wrote:
>>=20
>>> That seems like a very strange combination. If I remember correctly,
>>> packbits is a byte-based RLE scheme. Applied to floating point data,
>>> compression ought to be very inefficient.
>>=20
>> It may be a sensible option if the image has significant regions of
>> solid black.  The IEEE floating-point representation of 0.0 is: 0x00,
>> 0x00, 0x00, 0x00 (in either endian).
>=20
> Dictionary compressors are much more likely to win, overall. RLE does
> seem an odd choice, regardless of the actual data characteristics.
>=20
> --Toby
>=20
>>=20
>> --------------------------+----------------------
>> +--------------------------
>> Dr. Craig S. Bruce        | Ph 819-771-8303 x205 |
>> CubeWerx Inc.
>> Senior Software Developer |   Fax 819-771-8388   |  Gatineau,
>> Qu=E9bec, Canada
>> csbruce@cubewerx.com      |  http://csbruce.com/ |  http://
>> www.cubewerx.com/
>> --------------------------+----------------------
>> +--------------------------
>>              "Hard work may not kill you, but why take chances?"
>> _______________________________________________
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>=20
>=20
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