54 lines
1.4 KiB
PL/PgSQL
54 lines
1.4 KiB
PL/PgSQL
\set ON_ERROR_STOP on
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SET plpgsql.extra_errors TO 'all';
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drop function if exists detect_bends;
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-- detect_bends detects bends using the inflection angles. It does not do corrections.
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create or replace function detect_bends(line geometry, OUT bends geometry[]) as $$
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declare
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pi real;
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p geometry;
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p1 geometry;
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p2 geometry;
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p3 geometry;
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bend geometry;
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prev_sign int4;
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cur_sign int4;
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begin
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pi = radians(180);
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for p in (select (dp).geom from st_dumppoints(line) as dp) loop
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p3 = p2;
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p2 = p1;
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p1 = p;
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if p3 is null then
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continue;
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end if;
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cur_sign = sign(pi - st_angle(p1, p2, p2, p3));
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bend = st_linemerge(st_union(bend, st_makeline(p3, p2)));
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if prev_sign + cur_sign = 0 then
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if bend is not null then
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bends = bends || bend;
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end if;
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bend = st_makeline(p3, p2);
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end if;
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prev_sign = cur_sign;
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end loop;
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-- the last bend may be lost if there is no "final" inflection angle.
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-- to avoid that, return the last bend if the last accumulation has >3
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-- vertices.
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if (select count(1) from ((select st_dumppoints(bend) as a)) b) >= 3 then
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bends = bends || bend;
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end if;
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end
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$$ language plpgsql;
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-- fix_gentle_inflections moves bend endpoints following "Gentle Inflection at
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-- End of a Bend" section.
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create or replace function fix_gentle_inflections(INOUT bends geometry[]) as $$
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begin
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end
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$$ language plpgsql;
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