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Hello Simon,<br>
<br>
I'd like to add one point to Juan Lucas' hints:<br>
<br>
Testing Tif/GeoTiff you should add an appropriate amount of overviews
to it. This speeds up the performance significantly.<br>
<br>
<br>
Regards,<br>
Falk Krusche<br>
---<br>
MapConcept Ltd. - Kartographie und Geodatendienste
<br>
indigomap - Geoinformatik & Softwareentwicklung
<br>
<br>
04105 Leipzig, Gohliser Straße 13
<br>
fon +49 341 5614756
<br>
mobil +49 173 9146691
<br>
fax +49 341 5614758
<br>
<br>
<a class="moz-txt-link-abbreviated" href="http://www.mapconcept.de">www.mapconcept.de</a>
<br>
<a class="moz-txt-link-abbreviated" href="http://www.indigomap.de">www.indigomap.de</a>
<br>
<a class="moz-txt-link-abbreviated" href="http://www.kartenblatt.de">www.kartenblatt.de</a><br>
<br>
<br>
Juan Lucas Dominguez Rubio schrieb:
<blockquote
cite="mid:E43C32BC5843E34FB4C00CDFAAAAF7D8017B515E@australia.prodevelop.local"
type="cite">
<title>Re: [Gvsig_english] QUESTION gvSIG -- Image files with fast
rewrites</title>
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<meta content="MSHTML 6.00.6000.17080" name="GENERATOR">
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<div><font color="#000000" face="Times New Roman" size="3">Hello,
Simon.</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">Yes, I
have seen reasonably fast GeoTiff/TIF files. You will probably get one
of those by using the parameters suggested by Jukka Rahkonen.</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">As for the
comparison between image formats, I have done myself some tests, and my
current opinion is this:</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">JPG/JPEG:
very good compression ratio but very poor performance in terms of speed
and memory consumption. Should be used only for long term storage or
with very small images (for example, less than 5 megapixels, wich
includes tiles, as Google Maps does). Should not be used either for
very large images (for example, more than 50 megapixels) because the
amount of memory needed to manage them can be really scary. For small
images, it can be faster than ECW.</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">ECW: very
good compression ratio and very good performance in terms of memory
consumption and speed. Good for any image size. It's based on the
wavelets algorithm, and I suspect they have optimized significantly
their computations thanks to many years of experience and very skilled
C++ programmers.</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">JPEG2000:
Uses wavelets too, but in my (little) experience it's significantly
slower than ECW, probably due to lack of optimization.</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">GeoTiff,
TIF: Lots of different options when creating them. Very resonable
performance, I would say, though not as good as ECW in terms of
compression ratio and speed.</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">As far as
I know, JPG and ECW can only store RGB images, while GeoTiff can manage
other interesting data types (long integers, float, etc.)</font></div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">I don't
know the details, but I think one needs to acquire some kind of license
from Erdas (owner of the ECW format) when creating very large ECW
images (more than 170 megapixels, I think) for commercial purposes.</font></div>
<div> </div>
<div>When I talk about compression ratio, I'm assuming a similar
level of lossiness.</div>
<div> </div>
<div>Another relevant format is MrSid, which I pressume is very
similar to ECW, but less popular.</div>
<div> </div>
<div><font color="#000000" face="Times New Roman" size="3">All in
all, yes, I would say ECW is the best when using RGB images and
deserves recognition.</font></div>
<div> </div>
<div> </div>
<div>Regards,</div>
<div><font face="Courier New" size="2"><font face="Times New Roman"
size="3">Juan Lucas Domínguez Rubio<br>
</font>---</font></div>
</div>
<div id="idSignature88318">
<div><font face="Courier New" size="2"><font face="Courier New"
size="2"><font face="Courier New" size="2">Prodevelop SL, Valencia
(España)</font></font></font></div>
<div>
<div><font face="Courier New" size="2"><font face="Courier New"
size="2"><font face="Courier New" size="2">Tlf.: 96.351.06.12 -- Fax:
96.351.09.68<br>
</font><a moz-do-not-send="true" href="http://www.prodevelop.es/"><font
face="Courier New" size="2">http://www.prodevelop.es</font></a><br>
<font face="Courier New" size="2">---</font></font></font></div>
</div>
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<div><br>
<hr>
<font face="Tahoma" size="2"><b>De:</b>
<a class="moz-txt-link-abbreviated" href="mailto:gvsig_internacional-bounces@listserv.gva.es">gvsig_internacional-bounces@listserv.gva.es</a> en nombre de Simon Cropper<br>
<b>Enviado el:</b> mar 14/09/2010 14:52<br>
<b>Para:</b> Users and Developers mailing list<br>
<b>Asunto:</b> Re: [Gvsig_english] QUESTION gvSIG -- Image files with
fast rewrites<br>
</font><br>
</div>
<div>
<p><font size="2">Hi Juan Lucas,<br>
<br>
On Tuesday 14 September 2010 6:41:13 pm Juan Lucas Dominguez Rubio
wrote:<br>
> - If I remember it well, the gdal you get by using apt-get or
similar does<br>
> not include the ECW compressor, but I think the binaries from the
FWTools<br>
> website do, though I cannot test it right now:<br>
><br>
> <a moz-do-not-send="true"
href="http://home.gdal.org/fwtools/FWTools-linux-2.0.6.tar.gz">http://home.gdal.org/fwtools/FWTools-linux-2.0.6.tar.gz</a><br>
><br>
> Your experience suggests otherwise?<br>
<br>
Ubuntu GDAL libraries keep resetting to version without ECW. Even the
Ubuntu<br>
FWTools has reset. I keep setting up the system only to have it reset by<br>
itself.<br>
<br>
> Which error message do you get when trying to create a ECW?<br>
<br>
None really. It is just that the library does not recognise ECW format.<br>
<br>
> gdal_translate -of ecw image.jpg image.ecw<br>
<br>
Yeap. I found similar examples on the GDAL site and several HowTo
websites.<br>
<br>
The only way to get the FWTools to work was install it on a Windows
machine<br>
then using the export tool.<br>
<br>
> - Have you tried compressed TIF?<br>
<br>
No. Is it fast?<br>
<br>
Do you know of anyone who has compiled a matrix of image formats against<br>
compression, retention of image integrity (~loss of detail) and rewrite
time<br>
while panning (particularly in gvSIG)?<br>
<br>
ECW files are touted as the best compression-image quality
retention-rewrite<br>
combination: certainly in Australia it is the primary format used in
natural<br>
resource management by consultants and government agencies. Is this
hype, or<br>
does the format really hold the title?<br>
<br>
> ________________________________<br>
><br>
> De: <a class="moz-txt-link-abbreviated" href="mailto:gvsig_internacional-bounces@listserv.gva.es">gvsig_internacional-bounces@listserv.gva.es</a> en nombre de Simon
Cropper<br>
> (Botanicus Australia Pty Ltd) Enviado el: mar 14/09/2010 9:07<br>
> Para: Users and Developers mailing list<br>
> Asunto: [Gvsig_english] QUESTION gvSIG -- Image files with fast
rewrites<br>
><br>
><br>
><br>
> Hi,<br>
><br>
> Most of my clients provide aerial photography in ECW format. These
images<br>
> provide high resolution, are relatively small and quickly rewrite
on the<br>
> screen when panning.<br>
><br>
> Lately I have been getting JPG files. These files however are
quite big and<br>
> take significantly longer time to rewrite.<br>
><br>
> What is an alternative image format to ECW in the 'open free'
environment?<br>
> Something GDAL can be used to convert from JPG without jumping
through<br>
> hoops.<br>
><br>
> Ideally the file sizes should be low despite the high resolution,
gvSIG<br>
> able to read it natively and is quick to rewrite when panning.<br>
><br>
> Any suggestions would be appreciated.<br>
><br>
> PS. I know gdal_translate can, supposedly convert between JPG and
ECW, but<br>
> despite many attempts I have been unable to get this to work. I am
looking<br>
> for something else, if possible, that has the same intrinsic
properties<br>
> but is recognized by default in the gdal libraries so that every
time I<br>
> get an update of the 'free' Ubuntu version the FWTools or
alternative<br>
> 'commercially enabled' version is not replaced.<br>
<br>
--<br>
Cheers Simon<br>
<br>
Simon Cropper<br>
Botanicus Australia Pty Ltd<br>
PO Box 160 Sunshine 3020<br>
P: 03 9311 5822. M: 041 830 3437<br>
W: <a moz-do-not-send="true"
href="http://www.botanicusaustralia.com.au/">http://www.botanicusaustralia.com.au</a><br>
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