[postgis-users] Inconsistency between St_Value and ST_DumpAsPolygons

[Jean Marchal]

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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-- 
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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