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Merge pull request #259 from CartoDB/zoom_from_scale

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Use standard formula for CDB_ZoomFromScale
This commit is contained in:
Javier Goizueta
2016-05-27 16:15:42 +02:00
parent f5f59be5b0 2a30eb2fd3
commit 326aae4edb
1 changed files with 36 additions and 30 deletions
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66
scripts-available/CDB_ZoomFromScale.sql
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@@ -1,30 +1,36 @@
CREATE OR REPLACE FUNCTION cartodb.CDB_ZoomFromScale(scaleDenominator numeric) RETURNS int AS $$
BEGIN
CASE
WHEN scaleDenominator > 500000000 THEN RETURN 0;
WHEN scaleDenominator <= 500000000 AND scaleDenominator > 200000000 THEN RETURN 1;
WHEN scaleDenominator <= 200000000 AND scaleDenominator > 100000000 THEN RETURN 2;
WHEN scaleDenominator <= 100000000 AND scaleDenominator > 50000000 THEN RETURN 3;
WHEN scaleDenominator <= 50000000 AND scaleDenominator > 25000000 THEN RETURN 4;
WHEN scaleDenominator <= 25000000 AND scaleDenominator > 12500000 THEN RETURN 5;
WHEN scaleDenominator <= 12500000 AND scaleDenominator > 6500000 THEN RETURN 6;
WHEN scaleDenominator <= 6500000 AND scaleDenominator > 3000000 THEN RETURN 7;
WHEN scaleDenominator <= 3000000 AND scaleDenominator > 1500000 THEN RETURN 8;
WHEN scaleDenominator <= 1500000 AND scaleDenominator > 750000 THEN RETURN 9;
WHEN scaleDenominator <= 750000 AND scaleDenominator > 400000 THEN RETURN 10;
WHEN scaleDenominator <= 400000 AND scaleDenominator > 200000 THEN RETURN 11;
WHEN scaleDenominator <= 200000 AND scaleDenominator > 100000 THEN RETURN 12;
WHEN scaleDenominator <= 100000 AND scaleDenominator > 50000 THEN RETURN 13;
WHEN scaleDenominator <= 50000 AND scaleDenominator > 25000 THEN RETURN 14;
WHEN scaleDenominator <= 25000 AND scaleDenominator > 12500 THEN RETURN 15;
WHEN scaleDenominator <= 12500 AND scaleDenominator > 5000 THEN RETURN 16;
WHEN scaleDenominator <= 5000 AND scaleDenominator > 2500 THEN RETURN 17;
WHEN scaleDenominator <= 2500 AND scaleDenominator > 1500 THEN RETURN 18;
WHEN scaleDenominator <= 1500 AND scaleDenominator > 750 THEN RETURN 19;
WHEN scaleDenominator <= 750 AND scaleDenominator > 500 THEN RETURN 20;
WHEN scaleDenominator <= 500 AND scaleDenominator > 250 THEN RETURN 21;
WHEN scaleDenominator <= 250 AND scaleDenominator > 100 THEN RETURN 22;
WHEN scaleDenominator <= 100 THEN RETURN 23;
END CASE;
END
$$ LANGUAGE plpgsql IMMUTABLE;
-- Maximum supported zoom level
CREATE OR REPLACE FUNCTION _CDB_MaxSupportedZoom()
RETURNS int
LANGUAGE SQL
IMMUTABLE
AS $$
-- The maximum zoom level has to be limited for various reasons,
-- e.g. zoom levels greater than 31 would require tile coordinates
-- that would not fit in an INTEGER (which is signed, 32 bits long).
-- We'll choose 20 as a limit which is safe also when the JavaScript shift
-- operator (<<) is used for computing powers of two.
SELECT 29;
$$;
CREATE OR REPLACE FUNCTION cartodb.CDB_ZoomFromScale(scaleDenominator numeric)
RETURNS int
LANGUAGE SQL
IMMUTABLE
AS $$
SELECT
CASE
WHEN scaleDenominator > 600000000 THEN
-- Scale is smaller than zoom level 0
NULL
WHEN scaleDenominator = 0 THEN
-- Actual zoom level would be infinite
_CDB_MaxSupportedZoom()
ELSE
CAST (
LEAST(
ROUND(LOG(2, 559082264.028/scaleDenominator)),
_CDB_MaxSupportedZoom()
)
AS INTEGER)
END;
$$;