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Add another example to st_value demonstrating sampling and fix other example

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git-svn-id: http://svn.osgeo.org/postgis/trunk@5568 b70326c6-7e19-0410-871a-916f4a2858ee
This commit is contained in:
Regina Obe 2010-04-20 04:18:28 +00:00
parent 497206806f
commit b3b5b89e00
1 changed files with 46 additions and 13 deletions
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59
doc/reference_wktraster.xml
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@ -1213,7 +1213,7 @@ FROM (SELECT ST_Translate(ST_MakeEnvelope(
ST_UpperLeftX(rast) + ST_PixelSizeX(rast),
ST_UpperLeftY(rast) + ST_PixelSizeY(rast), 0
), ST_PixelSizeX(rast)*x, ST_PixelSizeY(rast)*y
) As pixpolyg, ST_Value(rast, 1, x, y) As b1val
) As pixpolyg, ST_Value(rast, 2, x, y) As b2val
FROM dummy_rast CROSS JOIN
generate_series(1,1000) As x CROSS JOIN generate_series(1,1000) As y
WHERE rid = 2
@ -1221,21 +1221,54 @@ WHERE rid = 2
WHERE
ST_Intersects(
pixpolyg,
ST_GeomFromText('POLYGON ((3427935.6902608695 5793250.889478261,
3427932.0770434784 5793251.682173912,
3427931.9295652173 5793250.400956522,
3427933.0576086957 5793248.985, 3427933.518478261 5793249.192391304,
3427934.611826087 5793248.999913043, 3427935.6902608695 5793250.889478261))',0)
) AND b1val != 254;
ST_GeomFromText('POLYGON((3427928 5793244,3427927.75 5793243.75,3427928 5793243.75,3427928 5793244))',0)
) AND b2val != 254;
shadow
------------------------------------------------------------------------------------
MULTIPOLYGON(((3427933.75 5793248.5,3427933.75 5793250,3427935.25 5793250,
3427935.25 5793248.5,3427933.75 5793248.5)),
((3427930.75 5793250,3427930.75 5793251.5,3427930.75 5793253,3427932.25 5793253,
3427932.25 5793251.5,3427932.25 5793250,3427930.75 5793250)),
((3427935.25 5793250,3427935.25 5793251.5,3427936.75 5793251.5,
3427936.75 5793250,3427935.25 5793250)))
MULTIPOLYGON(((3427928 5793243.9,3427928 5793243.85,3427927.95 5793243.85,3427927.95 5793243.9,
3427927.95 5793243.95,3427928 5793243.95,3427928.05 5793243.95,3427928.05 5793243.9,3427928 5793243.9)),((3427927.95 5793243.9,3427927.95 579324
3.85,3427927.9 5793243.85,3427927.85 5793243.85,3427927.85 5793243.9,3427927.9 5793243.9,3427927.9 5793243.95,
3427927.95 5793243.95,3427927.95 5793243.9)),((3427927.85 5793243.75,3427927.85 5793243.7,3427927.8 5793243.7,3427927.8 5793243.75
,3427927.8 5793243.8,3427927.8 5793243.85,3427927.85 5793243.85,3427927.85 5793243.8,3427927.85 5793243.75)),
((3427928.05 5793243.75,3427928.05 5793243.7,3427928 5793243.7,3427927.95 5793243.7,3427927.95 5793243.75,3427927.95 5793243.8,3427
927.95 5793243.85,3427928 5793243.85,3427928 5793243.8,3427928.05 5793243.8,
3427928.05 5793243.75)),((3427927.95 5793243.75,3427927.95 5793243.7,3427927.9 5793243.7,3427927.85 5793243.7,
3427927.85 5793243.75,3427927.85 5793243.8,3427927.85 5793243.85,3427927.9 5793243.85,
3427927.95 5793243.85,3427927.95 5793243.8,3427927.95 5793243.75)))
</programlisting>
<programlisting>
--- Checking all the pixels of a large raster tile can take a long time.
--- You can dramatically improve speed at some lose of precision by orders of magnitude
-- by sampling pixels using the step optional parameter of generate_series.
-- This next example does the same as previous but by checking 1 for every 4 (2x2) pixels and putting in the last checked
-- putting in the checked pixel as the value for subsequent 4
SELECT ST_AsText(ST_Union(pixpolyg)) As shadow
FROM (SELECT ST_Translate(ST_MakeEnvelope(
ST_UpperLeftX(rast), ST_UpperLeftY(rast),
ST_UpperLeftX(rast) + ST_PixelSizeX(rast)*2,
ST_UpperLeftY(rast) + ST_PixelSizeY(rast)*2, 0
), ST_PixelSizeX(rast)*x, ST_PixelSizeY(rast)*y
) As pixpolyg, ST_Value(rast, 2, x, y) As b2val
FROM dummy_rast CROSS JOIN
generate_series(1,1000,2) As x CROSS JOIN generate_series(1,1000,2) As y
WHERE rid = 2
AND x &lt;= ST_Width(rast) AND y &lt;= ST_Height(rast) ) As foo
WHERE
ST_Intersects(
pixpolyg,
ST_GeomFromText('POLYGON((3427928 5793244,3427927.75 5793243.75,3427928 5793243.75,3427928 5793244))',0)
) AND b2val != 254;
shadow
------------------------------------------------------------------------------------
MULTIPOLYGON(((3427927.9 5793243.85,3427927.8 5793243.85,3427927.8 5793243.95,
3427927.9 5793243.95,3427928 5793243.95,3427928.1 5793243.95,3427928.1 5793243.85,3427928 5793243.85,3427927.9 5793243.85)),
((3427927.9 5793243.65,3427927.8 5793243.65,3427927.8 5793243.75,3427927.8 5793243.85,3427927.9 5793243.85,
3427928 5793243.85,3427928 5793243.75,3427928.1 5793243.75,3427928.1 5793243.65,3427928 5793243.65,3427927.9 5793243.65)))
</programlisting>
</refsection>