[gdal-dev] Re: preserving alpha channel data with gdal_polygonize.py

[Chaitanya kumar CH]

Then, you can run a separate command to process the non-alpha bands.
You need two processes because there may not be one-to-one mapping of the
non-alpha and alpha band polygons.

Finally, you need to make intersections of the polygons in the two layers
and store the values of the alpha band polygons. I can't find any scripts
that do this. I'm afraid you need to do this yourselves.

On Tue, Jul 26, 2011 at 9:56 AM, Chaitanya kumar CH
<chaitanya.ch at gmail.com>wrote:

> John,
>
> gdal_polygonize script stores the common pixel value in a field for every
> polygon. By default it is named 'DN', which can be changed by specifying the
> fieldname option.
>
> You must use the alpha channel to polygonize. So you have to use the -b
> option to specify that and may have to use the -nomask option too.
>
>
> On Tue, Jul 26, 2011 at 9:21 AM, jt2000 <thakkar at nexgenwireless.com>wrote:
>
>> Thanks Jay,
>>
>> Ideally I would like the data to be in a column of the shapefile output so
>> I
>> can load it in the database and use it to query.  With gdal_polygonize.py
>> this doesn't seem possible so I was wondering what other options are out
>> there.
>>
>> --
>> View this message in context:
>> http://osgeo-org.1803224.n2.nabble.com/preserving-alpha-channel-data-with-gdal-transform-py-tp6620877p6620923.html
>> Sent from the GDAL - Dev mailing list archive at Nabble.com.
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>
>
>
>
> --
> Best regards,
> Chaitanya kumar CH.
>
> +91-9494447584
> 17.2416N 80.1426E
>



-- 
Best regards,
Chaitanya kumar CH.

+91-9494447584
17.2416N 80.1426E
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20110726/42e2d7bd/attachment.html