97 lines
2.4 KiB
MySQL
97 lines
2.4 KiB
MySQL
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--
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-- Fill given extent with a rectangular coverage
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--
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-- @param ext Extent to fill. Only rectangles with center point falling
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-- inside the extent (or at the lower or leftmost edge) will
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-- be emitted. The returned hexagons will have the same SRID
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-- as this extent.
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--
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-- @param width With of each rectangle
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--
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-- @param height Height of each rectangle
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--
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-- @param origin Optional origin to allow for exact tiling.
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-- If omitted the origin will be 0,0.
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-- The parameter is checked for having the same SRID
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-- as the extent.
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--
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--
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CREATE OR REPLACE FUNCTION CDB_RectangleGrid(ext GEOMETRY, width FLOAT8, height FLOAT8, origin GEOMETRY DEFAULT NULL)
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RETURNS SETOF GEOMETRY
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AS $$
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DECLARE
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h GEOMETRY; -- rectangle cell
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hstep FLOAT8; -- horizontal step
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vstep FLOAT8; -- vertical step
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hw FLOAT8; -- half width
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hh FLOAT8; -- half height
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vstart FLOAT8;
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hstart FLOAT8;
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hend FLOAT8;
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vend FLOAT8;
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xoff FLOAT8;
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yoff FLOAT8;
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xgrd FLOAT8;
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ygrd FLOAT8;
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x FLOAT8;
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y FLOAT8;
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srid INTEGER;
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BEGIN
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srid := ST_SRID(ext);
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xoff := 0;
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yoff := 0;
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IF origin IS NOT NULL THEN
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IF ST_SRID(origin) != srid THEN
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RAISE EXCEPTION 'SRID mismatch between extent (%) and origin (%)', srid, ST_SRID(origin);
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END IF;
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xoff := ST_X(origin);
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yoff := ST_Y(origin);
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END IF;
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--RAISE DEBUG 'X offset: %', xoff;
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--RAISE DEBUG 'Y offset: %', yoff;
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hw := width/2.0;
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hh := height/2.0;
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xgrd := hw;
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ygrd := hh;
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--RAISE DEBUG 'X grid size: %', xgrd;
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--RAISE DEBUG 'Y grid size: %', ygrd;
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hstep := width;
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vstep := height;
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-- Tweak horizontal start on hstep grid from origin
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hstart := xoff + ceil((ST_XMin(ext)-xoff)/hstep)*hstep;
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--RAISE DEBUG 'hstart: %', hstart;
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-- Tweak vertical start on vstep grid from origin
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vstart := yoff + ceil((ST_Ymin(ext)-yoff)/vstep)*vstep;
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--RAISE DEBUG 'vstart: %', vstart;
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hend := ST_XMax(ext);
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vend := ST_YMax(ext);
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--RAISE DEBUG 'hend: %', hend;
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--RAISE DEBUG 'vend: %', vend;
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x := hstart;
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WHILE x < hend LOOP -- over X
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y := vstart;
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h := ST_MakeEnvelope(x-hw, y-hh, x+hw, y+hh, srid);
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WHILE y < vend LOOP -- over Y
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RETURN NEXT h;
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h := ST_Translate(h, 0, vstep);
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y := yoff + round(((y + vstep)-yoff)/ygrd)*ygrd; -- round to grid
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END LOOP;
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x := xoff + round(((x + hstep)-xoff)/xgrd)*xgrd; -- round to grid
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END LOOP;
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RETURN;
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END
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$$ LANGUAGE 'plpgsql' IMMUTABLE;
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