2018.06.08 03:17 "Re: [Tiff] LZ4 compression", by fx HAYAKAWA MICHIO

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?

Thanks,
Michio

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

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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