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OK, looks like [3] for me. Thanks.<br>
<br>
On 7/28/2011 3:01 PM, Chaitanya kumar CH wrote:
<blockquote
cite="mid:CAMKgpOZqdEo1DqyeLRAKzV9mh+_HCxEosz0yz-O4q2Wtq8HG=Q@mail.gmail.com"
type="cite">The closest thing you can do without doing any coding
is to use the gdal_contour utility[1] to create a vector file and
then use gdal_rasterize [2] to burn them back to a raster. If you
use appropriate options, all your pixels will be clamped to the
discrete levels used in gdal_contour. It's straight forward to
apply a color table to that.<br>
<br>
If you want to do this using a script, refer to the gdal API
tutorial[3]. You'll have to do the classification while you read
and write the pixels using GDALRasterIO(). You can set the color
table too.<br>
<br>
Note that there may be some differences along the edges of
classified pixels between these two methods. The lines generated
by gdal_contour may go through the area of a pixel and could
change the burn value.<br>
<br>
[1]: <a moz-do-not-send="true"
href="http://www.gdal.org/gdal_contour.html">http://www.gdal.org/gdal_contour.html</a><br>
[2]: <a moz-do-not-send="true"
href="http://www.gdal.org/gdal_rasterize.html">http://www.gdal.org/gdal_rasterize.html</a><br>
[3]: <a moz-do-not-send="true"
href="http://www.gdal.org/gdal_tutorial.html">http://www.gdal.org/gdal_tutorial.html</a><br>
<br>
<div class="gmail_quote">On Fri, Jul 29, 2011 at 12:05 AM, Stephen
Crawford <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:src176@psu.edu">src176@psu.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000"> Thanks for the reply.
I had looked at these before, and then looked again after
your note, but I just don't understand how I map the climate
variable values to different colors in the palette, along
the lines of:<br>
<br>
tmax < 30 | color1<br>
30 < tmax < 50 | color2<br>
tmax > 50 | color3<br>
<br>
Thanks,<br>
Steve
<div>
<div class="h5"><br>
<br>
On 7/27/2011 1:01 AM, Chaitanya kumar CH wrote:
<blockquote type="cite">Sorry, here are the links.<br>
<br>
[1]: <a moz-do-not-send="true"
href="http://www.gdal.org/rgb2pct.html"
target="_blank">http://www.gdal.org/rgb2pct.html</a><br>
<br>
[2]: <a moz-do-not-send="true"
href="http://www.gdal.org/gdal_vrttut.html"
target="_blank">http://www.gdal.org/gdal_vrttut.html</a><br>
[3]: <a moz-do-not-send="true"
href="http://www.gdal.org/formats_list.html"
target="_blank">http://www.gdal.org/formats_list.html</a><br>
<br>
<div class="gmail_quote">On Wed, Jul 27, 2011 at 10:30
AM, Chaitanya kumar CH <span dir="ltr"><<a
moz-do-not-send="true"
href="http://chaitanya.ch" target="_blank">chaitanya.ch</a>@<a
moz-do-not-send="true" href="http://gmail.com"
target="_blank">gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt
0pt 0pt 0.8ex; border-left: 1px solid rgb(204,
204, 204); padding-left: 1ex;">Stephen,<br>
<br>
The docs for rgb2pct.py script [1] has an example
that shows how to convert to a paletted image
using hand made VRT file.<br>
You can use the "-of PNG" option to set the
destination format as png and the -pct option with
your VRT file.
<div>
<div><br>
<br>
<div class="gmail_quote">On Wed, Jul 27, 2011
at 2:42 AM, Stephen Crawford <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:src176@psu.edu"
target="_blank">src176@psu.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin: 0pt 0pt 0pt 0.8ex;
border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;"> Hi All,<br>
<br>
I have 60 or so asciiGrids of climate data
that I would like to tun into PNGs, with
the climate values classified by color. I
would like to script this process using
Python. Is there a way to do this with
GDAL? Or if not, is there any other open
source way to do this?<br>
<br>
Thanks,<br>
Steve<br>
<br>
<br>
_______________________________________________<br>
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href="mailto:gdal-dev@lists.osgeo.org"
target="_blank">gdal-dev@lists.osgeo.org</a><br>
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href="http://lists.osgeo.org/mailman/listinfo/gdal-dev"
target="_blank">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a><br>
</blockquote>
</div>
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</div>
<font color="#888888">-- <br>
Best regards,<br>
Chaitanya kumar CH.<br>
<br>
+91-9494447584<br>
17.2416N 80.1426E<br>
</font></blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
Best regards,<br>
Chaitanya kumar CH.<br>
<br>
+91-9494447584<br>
17.2416N 80.1426E<br>
</blockquote>
<br>
</div>
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<font color="#888888">
<pre cols="72">--
Stephen Crawford
Center for Environmental Informatics
The Pennsylvania State University
<a moz-do-not-send="true" href="mailto:src176@psu.edu" target="_blank">src176@psu.edu</a>
814.865.9905</pre>
</font></div>
</blockquote>
</div>
<br>
<br clear="all">
<br>
-- <br>
Best regards,<br>
Chaitanya kumar CH.<br>
<br>
+91-9494447584<br>
17.2416N 80.1426E<br>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
Stephen Crawford
Center for Environmental Informatics
The Pennsylvania State University
<a class="moz-txt-link-abbreviated" href="mailto:src176@psu.edu">src176@psu.edu</a>
814.865.9905</pre>
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