2019.03.30 14:06 "Re: [Tiff] combining TIFF images, not multi-page", by Kemp Watson

Paul, we have that functionality built into our converter, which takes strips of raster data and assembles them into a TIFF tiled pyramid, with minimal use of memory. Note that this becomes quite involved with unaligned input strips, dynamic conversion between raster and tile, and such.

We opted not to used libtiff, but it is perfectly capable of doing this, though not at a high level of abstraction. The devil is in the details, such as whether or not the strips are aligned in both x and y, or one, one none, and how the data will be fed into the system.

Yes, BigTIFF can have tiled pyramids – you can take a peek at our ZIF spec at http://zif.photo, might give you some thoughts; you might even be able to use the format.

Also, take a look at the Aperio.aci raw scanner format, if yours is anything like this, we probably already handle it, and might be able to help you avoid libtiff, *Magick, VIPS, etc.

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W. Kemp Watson
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Objective Pathology Services Limited
13629 Fallbrook Trail, Halton Hills
Ontario, Canada L7G 4S8

From: Tiff <tiff-bounces@lists.osgeo.org> on behalf of Paul Hemmer <paulhemmer@hotmail.com>

Thanks Bob.

As to the "low RAM footprint way" - in fact I am hoping to use the hard-drive instead of RAM. This is why I have a folder full of small partial images in the first place.

Even with a pyramidal representation, if I'm talking about a final image that may be several hundred gigabytes (or larger) in size, I could never assemble it all in memory in order to write the bottom layer of that pyramid. Can each resolution level be written in "tile by tile" or even line by line? Does this require a different API (like the ImageMagick API?) I assume as well that BigTIFF can be a tiled pyramid?

________________________________
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
Sent: Friday, March 29, 2019 7:02 PM

Subject: Re: [Tiff] combining TIFF images, not multi-page

On Fri, 29 Mar 2019, Paul Hemmer wrote:

> Hi, thanks for the reply!
>
> Do tiled TIFFs open and display as a single image? Do the tiles all
> have to be the same size? My images are broken into full-height
> "columns" of varying widths, that I want to concatenate all together
> into one image in a low-RAM footprint way.

Tiled TIFF does typically "open and display as a single image" but
this is a function of the reader. The reader might choose just to
display one tile, or the image portion corresponding to several tiles.
The tile size is fixed within a given TIFF image.

As has been subsquently mentioned, ImageMagick and GraphicsMagick
provide 'montage' functionality which can paste images together as you
describe, but they do not do so in a "low-RAM footprint way", unless
you are willing to use your hard drive in place of RAM.

If you are dealing with very large images, then it is common to use
tiled tiff with multiple resolutions of the same image so that the
viewer than see a zoomed-out image as well as zoom in to just part of
the image.