[gdal-dev] Polygonize from C# ?

[Luiz Motta]

Jay,

I made the plugin for QGIS, where, calculate the  boundary of image
with pixel value upper to zero, i believe is what you want,
"footprint shape".

The plugin read all images of directories and create one vector layer
with all boundary of images.

For calculate, the background of image need have pixel value equal a zero.

I wrote the program with  Python, but, i called the GDAL  functions
for calculus.

The name of plugin is "Image Boundary", and you can install inside
QGIS(contributed repository), or read the source by
http://spatialserver.net/pyqgis_1.0/contributed/imgboundary.zip

Regards,
Luiz Motta

2011/4/22 Jay Jennings <Jennings.Jay at geoeye.com>:
> Correct, we just need the footprint of the "good" (non-NODATA) area, which will often approximate a simple 4-point polygon with no holes.
>
> -----Original Message-----
> From: Elijah Robison [mailto:elijah at villagis.com]
> Sent: Friday, April 22, 2011 2:07 PM
> To: Jay Jennings
> Cc: gdal-dev at lists.osgeo.org
> Subject: Re: [gdal-dev] Polygonize from C# ?
>
> Jay, do you basically want a footprint shape of the useful data in the
> Sat images (say, without the collar), or is the problem more complex,
> where perhaps you have a mosaic of several images and, like swiss
> cheese, there are no-data holes within the image?
>
> It sounds to me like you just want a footprint of the collarless area;
> is this correct?
>
> /Elijah
>
> Jay Jennings wrote:
>> I see, thanks.  But since I have satellite images, this part of the doc is alarming: "...For non-thematic raster data (such as satellite images)
>> the result will essentially be one small polygon per pixel, and memory and output layer sizes will be substantial. The algorithm is primarily
>> intended for relatively simple thematic imagery, masks, and classification results".
>>
>> I just want one polygon enclosing the non-zero pixels (or alternatively, enclosing the zero pixels, then I could do a geometric
>> difference).  Is there any way to trick the method into doing that, to maybe avoid the heavy resource needs ?
>>
>>
>> -----Original Message-----
>> From: Even Rouault [mailto:even.rouault at mines-paris.org]
>> Sent: Friday, April 22, 2011 11:45 AM
>> To: Jay Jennings
>> Cc: gdal-dev at lists.osgeo.org
>> Subject: Re: [gdal-dev] Polygonize from C# ?
>>
>> Selon Jay Jennings <Jennings.Jay at geoeye.com>:
>>
>> Generally, refering to the C/C++ doc is a good way of finding the info :
>>
>> See http://gdal.org/gdal__alg_8h.html#3f522a9035d3512b5d414fb4752671b1
>>
>>
>>> Hi list,
>>> Can anyone point to any guidance or (preferably) examples on using
>>> GDAL.Polygonize() with C# bindings ?  I see what the interface is, but there
>>> are some unexplained parameters, e.g. "string[] options".
>>>
>>> My eventual goal is to open a raster and produce a WKT POLYGON string
>>> enclosing the "good" (non-NoData) area of the raster.  Thanks.
>>>
>>> .........................................................
>>> Jay Jennings
>>> Senior Software Developer
>>> (NASDAQ: GEOY)
>>> jennings.jay at geoeye.com
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
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>>
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