2018.06.08 03:31 "Re: [Tiff] LZ4 compression", by Kemp Watson

Adobe maintained two formal reservation lists, for TIFF tags, and for Compression schemes, as the official registries. They were removed about a year ago, and AFAIK no one has access or knows the content. There are hundreds or thousands of tags that have been properly reserved, that do not appear in the libtiff source code. all most unfortunate. Libtiff is in no way a source of truth for this. We really need to get a clear answer from Adobe about their position on support of TIFF from this point forward, and their intent for the registries, or accidental misuse _will_ occur and the whole system will fall apart.

Kemp

On Thu, Jun 7, 2018 at 11:17 PM, fx HAYAKAWA MICHIO < michio.hayakawa@fujixerox.co.jp> wrote:

>

I didn't check libtiff master repository at GitLab.
I believe reserving tags to avoid conflicts for feature enhancement is valuable. If Adobe get back, ask Adobe to approve them doesn't seem like a problem. Do you have any concerns about this strategy?

Cc: Even Rouault <even.rouault@spatialys.com>; tiff@lists.maptools.org

Subject: Re: [Tiff] LZ4 compression

Check what repository? I don't believe Adobe has got it back online yet - how can anyone register new tags when the registry has been removed? Does anyone even know what's in it?

Kemp

> On Thu, Jun 7, 2018 at 8:29 PM, fx HAYAKAWA MICHIO < > michio.hayakawa@fujixerox.co.jp <mailto:michio.hayakawa@fujixerox.co.jp>

> wrote:

Oh sorry, Even! I didn't check the repository.

How about followings?

#define COMPRESSION_LZ4         34927   /* LZ4 */

        #define TIFFTAG_LZ4QUALITY              65564   /* LZ4  acceleration factor */

Thanks,
Michio

-----Original Message-----

> From: Even Rouault [mailto:even.rouault@spatialys.com <mailto:
> even.rouault@spatialys.com> ]

To: tiff@lists.maptools.org <mailto:tiff@lists.maptools.org>

> Cc: fx HAYAKAWA MICHIO <michio.hayakawa@fujixerox.co.jp <mailto:
> michio.hayakawa@fujixerox.co.jp> >

Subject: Re: [Tiff] LZ4 compression

On vendredi 8 juin 2018 00:02:46 CEST fx HAYAKAWA MICHIO wrote:

> I successfully implemented LZ4 compression in libtiff on Windows platform.

LZ4 frame format is used for compression scheme. LZ4 frame is widely

> used for various applications.

Does anyone have any test images to see LZ4 compression characteristics?

I also modified tiffcp to support LZ4, so that any tiff files can be

converted into LZ4 tiff.

From my small experiments, its compression ratio is better than LZW,

> but worse than ZIP. Predictor is nicely working with LZ4. My tiff

> viewer shows

LZ4 tiff very fast compared to ZIP especially large tiff files. If

> someone want the code, I'd like to pick up two TAG values before

> releasing it to avoid confusion.

        > #define       COMPRESSION_LZ4         34926   /* LZ4 */
        > #define       TIFFTAG_LZ4QUALITY              65564   /* LZ4  acceleration factor */

Are there any objections to pick up those values?

Yes! libtiff master uses 34926 for ZSTD codec:

https://gitlab.com/libtiff/libtiff/blob/master/libtiff/tiff.h#L191 <https://gitlab.com/libtiff/libtiff/blob/master/libtiff/tiff.h#L191>

--

Spatialys - Geospatial professional services
http://www.spatialys.com

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