r.in/out.tiff has been updated by Luca Cristelli to optional tiled
TIFF support. It's in CVS now.
Markus
Here his mail:
On Fri, Feb 09, 2001 at 07:14:58PM +0100, Luca Cristelli wrote:
Hi Markus,
I hope you had a nice trip in Trento, I live 10km from Trento
in a small village. I had no possibility to attend the Grass Meeting
held there but I've heard it was great.
I attached the last revision of r.in.tiff and r.out.tiff with
full support for tiled tiff, both read and write. To test
the modules I created a lot of tiff files of varius types
(b/w, RGB, palette) and both modules work as expected.
My test pc is a Linux Debian (woody), kernel 2.2.18, gcc
I did a cvs-update some minutes ago and it seems there are
no conflicts.
Good work, Luca.
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I added tiled tiff support to r.in.tiff and r.out.tiff modules.
r.out.tiff has a new flag to force tiled tiff output:
-l
it forces 128x128 pixel tiles output
if the flag is not specified the module works the old way,
writing tiff files line by line (scanlines).
r.in.tiff detects automatically input tiff file type and
proceed accordingly so no specific flag is needed to read
tiled tiffs.
There are no particular improvements in writing speed, both
methods take the same. You get an enhancement when
reading very large tiff files and need only a
small region. If tiff file is organized by tiles it's
easy and fast to retrieve needed tiles. On the other side,
if tiff is scanline based it needs a lot more transfers
for the same task. If files are compressed this is even
more important.
I use a web/gis publishing software made by Autodesk called
MapGuide. I did some tests and tiled tiff are 10 to 100
times faster since MapGuide usually needs a small part of
the whole tiff.
The TIFF standard
[ http://partners.adobe.com/asn/developer/PDFS/TN/TIFF6.pdf ]
allows tiles of various sizes (even rectangular tiles)but 128x128
is a common value.
Also compression gains something from tiling. Usually compressing
tiffs by tile gives better results than by scanlines.
Greetings, Luca.
--------------------------------------------------------------
Luca Cristelli luca.cristelli@ies.it
I&S Informatica e Servizi www.ies.it
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