[postgis-users] Inconsistency between St_Value and ST_DumpAsPolygons

[dustymugs]

Can you file a ticket for this? Make sure to include your example. It
looks like something is wrong in GDAL's GDALFPolygonize() function.

-bborie

On 06/06/2013 01:50 PM, Jean Marchal wrote:
> I am using GDAL 1.9.2, yep ST_PixelAsPolygons() works fine,
> 
> Jean
> 
> 2013/6/6 dustymugs <dustymugs at gmail.com>
> 
>> What version of GDAL are you using? ST_DumpAsPolygons() uses GDAL for
>> processing. I notice that ST_PixelAsPolygons() works correctly...
>>
>> -bborie
>>
>> On 06/06/2013 01:04 PM, Jean Marchal wrote:
>>> Bborie,
>>>
>>> I used ST_Value to prove that the value for pixel with coordinates (8,2)
>>> does exist. I did not mention it but adjacent pixels contains different
>>> values (see reproducible example).
>>>
>>> Jean
>>>
>>> 2013/6/6 Bborie Park <dustymugs at gmail.com>
>>>
>>>> ST_Value and ST_DumpAsPolygons do very different things. ST_Value gets a
>>>> value for a specific pixel while ST_DumpAsPolygons() dumps values by
>>>> merging pixels with same value in an area.
>>>>
>>>> -bborie
>>>>
>>>>
>>>> On Thu, Jun 6, 2013 at 12:38 PM, Jean Marchal <jean.d.marchal at gmail.com
>>> wrote:
>>>>
>>>>> Dear List,
>>>>>
>>>>> value's number 4 in this raster come out with ST_Value:
>>>>>
>>>>> SELECT ST_Value(rast, 1, 8, 2), ST_BandnoDataValue(rast),
>>>>> ST_BandPixelType(rast)
>>>>> FROM (SELECT '
>>>>>
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raster
>>>>> rast) foo
>>>>>
>>>>> but not with ST_DumpAsPolygons:
>>>>>
>>>>> SELECT (ST_DumpAsPolygons(rast)).val
>>>>> FROM (SELECT
>>>>>
>> '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'::raster
>>>>> rast) foo
>>>>>
>>>>> Is this a bug or I am doing something wrong ?
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Jean
>>>>>
>>>>> --
>>>>> Jean Marchal
>>>>>
>>>>> Etudiant au doctorat / PHD student
>>>>> Université Laval - Pavillon Abitibi-Price
>>>>> Faculté de foresterie, de géographie et de géomatique
>>>>> 2405, rue de la Terrasse
>>>>> Québec (Québec) G1V 0A6
>>>>>
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>>>>>
>>>>
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