2018.05.11 21:58 "Re: [Tiff] LZ4 compression", by Kemp Watson

Yes, it is registered with Adobe, although I had to put it in the private tag area, as there is no mechanism for adding revisions to the standard.... so anyone else can add PNG, and we'll get duplicate tags. I know I'm cranky about this, but this is an example of why a solid registry is so important. We added JPEG-XR as well; there are at least 3 tags in common use for JPEG 2000, probably more, only one is actually registered.

We use PNG because ZIF is browser-friendly, so LZW/Deflate etc don't apply to the intended use.

Yes, two subcommunities, so no disaster; but a bit of a lost opportunity to build a common base together. We should track the projects, maybe there's value in each to be shared.

W. Kemp Watson
Objective Pathology Services Limited
Halton Data Center
8250 Lawson Road
Milton, Ontario
Canada L9T 5C6

http://www.objectivepathology.com

kemp@objectivepathology.com
tel. +1 (416) 970-7284

> On May 11, 2018, at 5:15 PM, Even Rouault <even.rouault@spatialys.com> wrote:

On vendredi 11 mai 2018 16:54:00 CEST Kemp Watson wrote:

Interesting about cloud-optimized GeoTIFF; I wasn't aware of the project - we've been doing exactly that for 12 years with our ZIF format (although we used to need a bit of server-side Javascript before range-requests, in the pre-BigTIFF version). See http://zif.photo.

Ah I'm discovering ZIF...

I see that you use Compression=34933 for PNG. Is that officially registered? Anyway, would be worth having it 'reserved' in tiff.h (I guess libtiff can be a decent registry...). Do you mind issuing a pull request for that, so at least no one steps over that one?

From your experience, PNG offers better compression than DEFLATE? Probably due to the 2D filters?

For COG, a JavaScript client has been released just yesterday: https://geotiffjs.github.io/cog-explorer/

So much duplication of effort since the Internet - connection is not communication.

Was probably worse *before* the Internet :-)

The issue here is that we belong to 2 different 'sub-communities' of TIFF, which makes unwanted fragmentation more prone.