[gdal-dev] Polygonize from C# ?

[Jay Jennings]

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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