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Date: Thu, 30 Sep 2021 10:06:10 +0100
From: Roger Leigh <rleigh@codelibre.net>
To: Kemp Watson <kemp@objectivepathology.com>,
 Even Rouault <even.rouault@spatialys.com>
CC: "tiff@lists.osgeo.org" <tiff@lists.osgeo.org>,
 "geotiff.swg@lists.ogc.org" <geotiff.swg@lists.ogc.org>
Message-ID: <10790B38-0380-4FEC-B368-E5873B83580A@codelibre.net>
Thread-Topic: [Tiff] Proposal to create a OGC BigTIFF standard
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Subject: Re: [Tiff] Proposal to create a OGC BigTIFF standard
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Hi Kemp,

=20

=20

While not strictly related to =E2=80=9CBigTIFF=E2=80=9D, but certainly related to =E2=80=9CBi=
g=E2=80=9D images, there is one big gap which would be useful to close to better m=
eet the needs of medical and scientific imaging, and that is standardising f=
ull support for storing 3D image data.=C2=A0 Libtiff does have some non-standard=
 tags for this purpose, but for reasons of compatibility with other tools, I=
 have never used them.=C2=A0 Were they to be more formally recognised and adopte=
d, storing volumetric data would become both practical and accessible.=C2=A0 Thi=
s is one of the main reasons for the adoption of other file formats for this=
 type of data, despite TIFF being a perfectly suitable container.=C2=A0 But TIFF=
 is perfectly capable of this.

=20

I=E2=80=99m thinking here of the addition of a Z dimension at both the image and =
tile level, with:

=20

TIFFTAG_IMAGEDEPTH

TIFFTAG_TILEDEPTH

TIFFTAG_ZRESOLUTION

TIFFTAG_ZPOSITION

=20

This would be the minimum required.=C2=A0 And it=E2=80=99s already fully implemented =
as far as I can tell, unless other tags need extending for an optional third=
 value which haven=E2=80=99t been done yet.=C2=A0 If we could get this standardised th=
at would be huge.

=20

And others, e.g.

=20

TIFFTAG_ZCLIPPATHUNITS ?? =C2=A0Probably a can of worms to extend to 3D!

EXIFTAG_PIXELZDIMENSION ??=C2=A0 Probably not needed if EXIF is restricted to 2=
D?

=20

=20

Aside: I saw TIFFTAG_XCLIPPATHUNITS duplicated in tif_dirinfo.c.=C2=A0 With dif=
ferent types (SLONG and SBYTE).=C2=A0 Is that a bug?=C2=A0 Or intentional?=C2=A0=C2=A0 TIFFT=
AG_YCLIPPATHUNITS is not duplicated.

=20

=20

Kind regards,

Roger

=20

On 28/09/2021, 16:08, "Tiff on behalf of Kemp Watson via Tiff" <tiff-bounce=
s@lists.osgeo.org on behalf of tiff@lists.osgeo.org> wrote:

=20

Hi Even et al:

=20

To my knowledge, the community that was behind the BigTIFF specification is=
 now effectively Leica (medical, not Geosystems).

The initial specification came from Ole Eichhorn, then at Aperio, a digital=
 pathology company which was acquired by Leica.

The involvement of Aware systems as far as I know was only hosting a discus=
sion on their mailing list, and documenting essentially a copy of Ole's work=
. I don't believe the participants were from Aware.

Anyone do please correct me if my understanding is incomplete or incorrect.

=20

However, this unofficial specification only covers a migration of TIFF to 6=
4-bits, and says nothing in particular about tiling, multi-resolutions, mult=
i-channels, bit depths, compression, TIFFtags/metadata, etc, all of which ne=
ed to be defined per application at a higher level.

Various stabs at this for multiresolution imaging have been made over the y=
ears: Aperio.svs, COG, ZIF (my own), OME-TIFF (used ZIF as a reference point=
), and many 99% similar flavors of pyramidal tiled (big)TIFF. Shame we can't=
 all get it together.

=20

Given that GeoTIFF and COG specifications exist, what is OGC intending to a=
dd beyond that? Is it just the "64-bit"ness, or metadata?

=20

There is no formal maintainer; the AWARE systems site does not maintain the=
 BigTIFF specification, that is just a reference; another is at http://bigti=
ff.org, a site now owned by Leica.

=20

And I'm not sure the wording on https://github.com/opengeospatial/BigTIFF i=
s as intended?: "it becomes an OGC standard" sounds like OGC intends to take=
 over ownership of BigTIFF? Leica might have something to say about that, al=
though the specification has been put in the public domain.

Personally, I really wish Adobe as the owner of the TIFF specification woul=
d step up to the plate with this, and update the actual TIFF specification t=
o cover BigTIFF. Their focus has been elsewhere for many years, but this wou=
ld be a great community service.

=20

Regards,

=20

Kemp Watson

Objective Pathology Services

Toronto, Canada

=20

=20

=20

On Tue, Sep 28, 2021 at 9:52 AM Even Rouault <even.rouault@spatialys.com> w=
rote:

Hi,

A group of people (to which I belong to) in the Open Geospatial Consortium =
(OGC, www.ogc.org) would like to move the BigTIFF specification into the OGC=
 standards process. The intention is to create a OGC standard that is fully =
compatible with the existing documentation and implementation of BigTIFF. We=
 would like to do this in a open process and make sure that the community th=
at was behind the BigTIFF specification are invited to participate in the pr=
ocess and are well recognized for their previous work. The OGC will provide =
a process to maintain the standard in the future and will work to make GeoTI=
FF and Cloud Optimized GeoTIFF (COG) standards to support both TIFF and BigT=
IFF. All OGC standards are available for free in the OGC website.

The process will be done in a open GitHub repository and the first attempt =
can be found here: https://github.com/opengeospatial/BigTIFF
You are invited to submit issues or to create pull requests as part of the =
way to provided comments and improve the standard draft.

Is there any objection or comment before we start this process?

Best regards,

Even
--=20
http://www.spatialys.com
My software is free, but my time generally not.
_______________________________________________
Tiff mailing list
Tiff@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/tiff

_______________________________________________ Tiff mailing list Tiff@list=
s.osgeo.org https://lists.osgeo.org/mailman/listinfo/tiff=20


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<html xmlns:o=3D"urn:schemas-microsoft-com:office:office" xmlns:w=3D"urn:schema=
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04/12/omml" xmlns=3D"http://www.w3.org/TR/REC-html40"><head><meta http-equiv=3DC=
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--></style></head><body lang=3DEN-GB link=3Dblue vlink=3Dpurple style=3D'word-wrap:=
break-word'><div class=3DWordSection1><p class=3DMsoNormal><span style=3D'mso-fare=
ast-language:EN-US'>Hi Kemp,<o:p></o:p></span></p><p class=3DMsoNormal><span s=
tyle=3D'mso-fareast-language:EN-US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNo=
rmal><span style=3D'mso-fareast-language:EN-US'><o:p>&nbsp;</o:p></span></p><p=
 class=3DMsoNormal><span style=3D'mso-fareast-language:EN-US'>While not strictly=
 related to =E2=80=9CBigTIFF=E2=80=9D, but certainly related to =E2=80=9CBig=E2=80=9D images, there =
is one big gap which would be useful to close to better meet the needs of me=
dical and scientific imaging, and that is standardising full support for sto=
ring 3D image data.=C2=A0 Libtiff does have some non-standard tags for this purp=
ose, but for reasons of compatibility with other tools, I have never used th=
em.=C2=A0 Were they to be more formally recognised and adopted, storing volumetr=
ic data would become both practical and accessible.=C2=A0 This is one of the mai=
n reasons for the adoption of other file formats for this type of data, desp=
ite TIFF being a perfectly suitable container.=C2=A0 But TIFF is perfectly capab=
le of this.<o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast=
-language:EN-US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span style=3D=
'mso-fareast-language:EN-US'>I=E2=80=99m thinking here of the addition of a Z dime=
nsion at both the image and tile level, with:<o:p></o:p></span></p><p class=3D=
MsoNormal><span style=3D'mso-fareast-language:EN-US'><o:p>&nbsp;</o:p></span><=
/p><p class=3DMsoNormal><span style=3D'mso-fareast-language:EN-US'>TIFFTAG_IMAGE=
DEPTH<o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-langu=
age:EN-US'>TIFFTAG_TILEDEPTH<o:p></o:p></span></p><p class=3DMsoNormal><span s=
tyle=3D'mso-fareast-language:EN-US'>TIFFTAG_ZRESOLUTION<o:p></o:p></span></p><=
p class=3DMsoNormal><span style=3D'mso-fareast-language:EN-US'>TIFFTAG_ZPOSITION=
<o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-language:E=
N-US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareas=
t-language:EN-US'>This would be the minimum required.=C2=A0 And it=E2=80=99s already f=
ully implemented as far as I can tell, unless other tags need extending for =
an optional third value which haven=E2=80=99t been done yet.=C2=A0 If we could get thi=
s standardised that would be huge.<o:p></o:p></span></p><p class=3DMsoNormal><=
span style=3D'mso-fareast-language:EN-US'><o:p>&nbsp;</o:p></span></p><p class=
=3DMsoNormal><span style=3D'mso-fareast-language:EN-US'>And others, e.g.<o:p></o=
:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-language:EN-US'><o=
:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-langua=
ge:EN-US'>TIFFTAG_ZCLIPPATHUNITS ?? =C2=A0Probably a can of worms to extend to 3=
D!<o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-language=
:EN-US'>EXIFTAG_PIXELZDIMENSION ??=C2=A0 Probably not needed if EXIF is restrict=
ed to 2D?<o:p></o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-l=
anguage:EN-US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span style=3D'm=
so-fareast-language:EN-US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><s=
pan style=3D'mso-fareast-language:EN-US'>Aside: I saw TIFFTAG_XCLIPPATHUNITS d=
uplicated in tif_dirinfo.c.=C2=A0 With different types (SLONG and SBYTE).=C2=A0 Is t=
hat a bug?=C2=A0 Or intentional?=C2=A0=C2=A0 TIFFTAG_YCLIPPATHUNITS is not duplicated.<o=
:p></o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-language:EN-=
US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span style=3D'mso-fareast-=
language:EN-US'><o:p>&nbsp;</o:p></span></p><p class=3DMsoNormal><span style=3D'=
mso-fareast-language:EN-US'>Kind regards,<o:p></o:p></span></p><p class=3DMsoN=
ormal><span style=3D'mso-fareast-language:EN-US'>Roger<o:p></o:p></span></p><p=
 class=3DMsoNormal><span style=3D'mso-fareast-language:EN-US'><o:p>&nbsp;</o:p><=
/span></p><div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>On 28/09/2=
021, 16:08, &quot;Tiff on behalf of Kemp Watson via Tiff&quot; &lt;<a href=3D"=
mailto:tiff-bounces@lists.osgeo.org">tiff-bounces@lists.osgeo.org</a> on beh=
alf of <a href=3D"mailto:tiff@lists.osgeo.org">tiff@lists.osgeo.org</a>&gt; wr=
ote:<o:p></o:p></p></div></div><div><p class=3DMsoNormal style=3D'margin-left:36=
.0pt'><o:p>&nbsp;</o:p></p></div><div><div><p class=3DMsoNormal style=3D'margin-=
left:36.0pt'>Hi Even et al:<o:p></o:p></p></div><div><p class=3DMsoNormal styl=
e=3D'margin-left:36.0pt'><o:p>&nbsp;</o:p></p></div><div><p class=3DMsoNormal st=
yle=3D'margin-left:36.0pt'>To my knowledge, the community that was behind the =
BigTIFF specification is now effectively Leica (medical, not Geosystems).<o:=
p></o:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>The ini=
tial specification came from Ole Eichhorn, then at Aperio, a digital patholo=
gy company which was acquired by Leica.<o:p></o:p></p></div><div><p class=3DMs=
oNormal style=3D'margin-left:36.0pt'>The involvement of Aware systems as far a=
s I know was only hosting a discussion on their mailing list, and documentin=
g essentially a copy of Ole's work. I don't believe the participants were fr=
om Aware.<o:p></o:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.=
0pt'>Anyone do please correct me if my understanding is incomplete or incorr=
ect.<o:p></o:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>=
<o:p>&nbsp;</o:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt=
'>However, this unofficial specification only covers a migration of TIFF to =
64-bits, and says nothing in particular about tiling, multi-resolutions, mul=
ti-channels, bit depths, compression, TIFFtags/metadata, etc, all of which n=
eed to be defined per application at a higher level.<o:p></o:p></p></div><di=
v><p class=3DMsoNormal style=3D'margin-left:36.0pt'>Various stabs at this for mu=
ltiresolution imaging have been made over the years: Aperio.svs, COG, ZIF (m=
y own), OME-TIFF (used ZIF as a reference point), and many 99% similar flavo=
rs of pyramidal tiled (big)TIFF. Shame we can't all get it together.<o:p></o=
:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'><o:p>&nbsp;<=
/o:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>Given that=
 GeoTIFF and COG specifications exist, what is OGC intending to add beyond t=
hat? Is it just the &quot;64-bit&quot;ness, or metadata?<o:p></o:p></p></div=
><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'><o:p>&nbsp;</o:p></p></d=
iv><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>There is no formal mai=
ntainer; the AWARE systems site does not maintain the BigTIFF specification,=
 that is just a reference; another is at <a href=3D"http://bigtiff.org">http:/=
/bigtiff.org</a>, a site now owned by Leica.<o:p></o:p></p></div><div><p cla=
ss=3DMsoNormal style=3D'margin-left:36.0pt'><o:p>&nbsp;</o:p></p></div><div><p c=
lass=3DMsoNormal style=3D'margin-left:36.0pt'>And I'm not sure the wording on <a=
 href=3D"https://github.com/opengeospatial/BigTIFF">https://github.com/opengeo=
spatial/BigTIFF</a> is as intended?: &quot;it becomes an OGC standard&quot; =
sounds like OGC intends to take over ownership of BigTIFF? Leica might have =
something to say about that, although the specification has been put in the =
public domain.<o:p></o:p></p></div><div><p class=3DMsoNormal style=3D'margin-lef=
t:36.0pt'>Personally, I really wish Adobe as the owner of the TIFF specifica=
tion would step up to the plate with this, and update the actual TIFF specif=
ication to cover BigTIFF. Their focus has been elsewhere for many years, but=
 this would be a great community service.<o:p></o:p></p></div><div><p class=3D=
MsoNormal style=3D'margin-left:36.0pt'><o:p>&nbsp;</o:p></p></div><div><p clas=
s=3DMsoNormal style=3D'margin-left:36.0pt'>Regards,<o:p></o:p></p></div><div><p =
class=3DMsoNormal style=3D'margin-left:36.0pt'><o:p>&nbsp;</o:p></p></div><div><=
p class=3DMsoNormal style=3D'margin-left:36.0pt'>Kemp Watson<o:p></o:p></p></div=
><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>Objective Pathology Serv=
ices<o:p></o:p></p></div><div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>=
Toronto, Canada<o:p></o:p></p></div><div><p class=3DMsoNormal style=3D'margin-le=
ft:36.0pt'><o:p>&nbsp;</o:p></p></div><div><p class=3DMsoNormal style=3D'margin-=
left:36.0pt'><o:p>&nbsp;</o:p></p></div></div><p class=3DMsoNormal style=3D'marg=
in-left:36.0pt'><o:p>&nbsp;</o:p></p><div><div><p class=3DMsoNormal style=3D'mar=
gin-left:36.0pt'>On Tue, Sep 28, 2021 at 9:52 AM Even Rouault &lt;<a href=3D"m=
ailto:even.rouault@spatialys.com">even.rouault@spatialys.com</a>&gt; wrote:<=
o:p></o:p></p></div><blockquote style=3D'border:none;border-left:solid #CCCCCC=
 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm'><div><p=
 style=3D'margin-left:36.0pt'>Hi,<o:p></o:p></p><p style=3D'margin-left:36.0pt'>=
A group of people (to which I belong to) in the Open Geospatial Consortium (=
OGC, <a href=3D"http://www.ogc.org" target=3D"_blank">www.ogc.org</a>) would lik=
e to move the BigTIFF specification into the OGC standards process. The inte=
ntion is to create a OGC standard that is fully compatible with the existing=
 documentation and implementation of BigTIFF. We would like to do this in a =
open process and make sure that the community that was behind the BigTIFF sp=
ecification are invited to participate in the process and are well recognize=
d for their previous work. The OGC will provide a process to maintain the st=
andard in the future and will work to make GeoTIFF and Cloud Optimized GeoTI=
FF (COG) standards to support both TIFF and BigTIFF. All OGC standards are a=
vailable for free in the OGC website.<o:p></o:p></p><p style=3D'margin-left:36=
.0pt'>The process will be done in a open GitHub repository and the first att=
empt can be found here: <a href=3D"https://github.com/opengeospatial/BigTIFF" =
target=3D"_blank">https://github.com/opengeospatial/BigTIFF</a><br>You are inv=
ited to submit issues or to create pull requests as part of the way to provi=
ded comments and improve the standard draft.<o:p></o:p></p><p style=3D'margin-=
left:36.0pt'>Is there any objection or comment before we start this process?=
<o:p></o:p></p><p style=3D'margin-left:36.0pt'>Best regards,<o:p></o:p></p><p =
style=3D'margin-left:36.0pt'>Even<o:p></o:p></p><pre style=3D'margin-left:36.0pt=
'>-- <o:p></o:p></pre><pre style=3D'margin-left:36.0pt'><a href=3D"http://www.sp=
atialys.com" target=3D"_blank">http://www.spatialys.com</a><o:p></o:p></pre><p=
re style=3D'margin-left:36.0pt'>My software is free, but my time generally not=
.<o:p></o:p></pre></div><p class=3DMsoNormal style=3D'margin-left:36.0pt'>______=
_________________________________________<br>Tiff mailing list<br><a href=3D"m=
ailto:Tiff@lists.osgeo.org" target=3D"_blank">Tiff@lists.osgeo.org</a><br><a h=
ref=3D"https://lists.osgeo.org/mailman/listinfo/tiff" target=3D"_blank">https://=
lists.osgeo.org/mailman/listinfo/tiff</a><o:p></o:p></p></blockquote></div><=
p class=3DMsoNormal style=3D'margin-left:36.0pt'>_______________________________=
________________ Tiff mailing list Tiff@lists.osgeo.org https://lists.osgeo.=
org/mailman/listinfo/tiff <o:p></o:p></p></div></body></html>

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