<para>
<xref linkend="UpdateGeometrySRID"/>
</para>
+ </refsection>
+ </refentry>
+
+ <refentry id="RT_Retile">
+ <refnamediv>
+ <refname>ST_Retile</refname>
+ <refpurpose>
+ Return a set of configured tiles from an arbitrarily tiled raster coverage.
+ </refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+
+ <funcprototype>
+ <funcdef>SETOF raster <function>ST_Retile</function></funcdef>
+ <paramdef><type>regclass </type> <parameter>tab</parameter></paramdef>
+ <paramdef><type>name </type> <parameter>col</parameter></paramdef>
+ <paramdef><type>geometry </type> <parameter>ext</parameter></paramdef>
+ <paramdef><type>float8 </type> <parameter>sfx</parameter></paramdef>
+ <paramdef><type>float8 </type> <parameter>sfy</parameter></paramdef>
+ <paramdef><type>int </type> <parameter>tw</parameter></paramdef>
+ <paramdef><type>int </type> <parameter>th</parameter></paramdef>
+ <paramdef choice="opt"><type>text </type> <parameter>algo='NearestNeighbor'</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsection>
+ <title>Description</title>
+
+ <para>
+Return a set of tiles having the specified scale (<varname>sfx</varname>,
+<varname>sfy</varname>) and max size (<varname>tw</varname>,
+<varname>th</varname>) and covering the specified extent
+(<varname>ext</varname>) with data coming from the specified
+raster coverage (<varname>tab</varname>, <varname>col</varname>).
+ </para>
+
+ <para>Algorithm options are: 'NearestNeighbor', 'Bilinear', 'Cubic', 'CubicSpline', and 'Lanczos'. Refer to: <ulink url="http://www.gdal.org/gdalwarp.html">GDAL Warp resampling methods</ulink> for more details.</para>
+
+ <para>Availability: 2.2.0</para>
+ </refsection>
+ <refsection>
+ <title>See Also</title>
+ <para>
+ <xref linkend="RT_CreateOverview"/>
+ </para>
+ </refsection>
+ </refentry>
+
+ <refentry id="RT_CreateOverview">
+ <refnamediv>
+ <refname>ST_CreateOverview</refname>
+ <refpurpose>
+Create an reduced resolution version of a given raster coverage.
+ </refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+
+ <funcprototype>
+ <funcdef>regclass <function>ST_CreateOverview</function></funcdef>
+ <paramdef><type>regclass </type> <parameter>tab</parameter></paramdef>
+ <paramdef><type>name </type> <parameter>col</parameter></paramdef>
+ <paramdef><type>int </type> <parameter>factor</parameter></paramdef>
+ <paramdef choice="opt"><type>text </type> <parameter>algo='NearestNeighbor'</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsection>
+ <title>Description</title>
+
+ <para>
+Create an overview table with resampled tiles from the source table.
+Output tiles will have the same size of input tiles and cover the same
+spatial extent with a lower resolution (pixel size will be
+1/<varname>factor</varname> of the original in both directions).
+ </para>
+
+ <para>
+The overview table will be made available in the
+<varname>raster_overviews</varname> catalog and will have raster
+constraints enforced.
+ </para>
+
+ <para>Algorithm options are: 'NearestNeighbor', 'Bilinear', 'Cubic', 'CubicSpline', and 'Lanczos'. Refer to: <ulink url="http://www.gdal.org/gdalwarp.html">GDAL Warp resampling methods</ulink> for more details.</para>
+
+ <para>Availability: 2.2.0</para>
+ </refsection>
+ <refsection>
+ <title>See Also</title>
+ <para>
+ <xref linkend="RT_Retile"/>,
+ <xref linkend="RT_AddOverviewConstraints"/>,
+ <xref linkend="RT_AddRasterConstraints"/>,
+ <xref linkend="RT_Raster_Overviews"/>
+ </para>
</refsection>
</refentry>
</sect1>
AS $$ SELECT _UpdateRasterSRID('', $1, $2, $3) $$
LANGUAGE 'sql' VOLATILE STRICT;
+------------------------------------------------------------------------------
+-- ST_Retile
+------------------------------------------------------------------------------
+
+-- Availability: 2.2.0
+-- @param ext extent to create overviews for, also used for grid origin
+-- SRID must match source tile srid.
+-- @param sfx scale factor x (pixel width)
+-- @param sfy scale factor y (pixel height, usually negative)
+-- @param tw max tile width
+-- @param th max tile height
+--
+CREATE OR REPLACE FUNCTION ST_Retile(tab regclass, col name, ext geometry, sfx float8, sfy float8, tw int, th int, algo text DEFAULT 'NearestNeighbour')
+RETURNS SETOF raster AS $$
+DECLARE
+ rec RECORD;
+ ipx FLOAT8;
+ ipy FLOAT8;
+ tx int;
+ ty int;
+ te GEOMETRY; -- tile extent
+ ncols int;
+ nlins int;
+ srid int;
+ sql TEXT;
+BEGIN
+
+ RAISE DEBUG 'Target coverage will have sfx=%, sfy=%', sfx, sfy;
+
+ -- 2. Loop over each target tile and build it from source tiles
+ ipx := st_xmin(ext);
+ ncols := ceil((st_xmax(ext)-ipx)/sfx/tw);
+ IF sfy < 0 THEN
+ ipy := st_ymax(ext);
+ nlins := ceil((st_ymin(ext)-ipy)/sfy/th);
+ ELSE
+ ipy := st_ymin(ext);
+ nlins := ceil((st_ymax(ext)-ipy)/sfy/th);
+ END IF;
+
+ srid := ST_Srid(ext);
+
+ RAISE DEBUG 'Target coverage will have % x % tiles, each of approx size % x %', ncols, nlins, tw, th;
+ RAISE DEBUG 'Target coverage will cover extent %', ext::box2d;
+
+ FOR tx IN 0..ncols-1 LOOP
+ FOR ty IN 0..nlins-1 LOOP
+ te := ST_MakeEnvelope(ipx + tx * tw * sfx,
+ ipy + ty * th * sfy,
+ ipx + (tx+1) * tw * sfx,
+ ipy + (ty+1) * th * sfy,
+ srid);
+ --RAISE DEBUG 'sfx/sfy: %, %', sfx, sfy;
+ --RAISE DEBUG 'tile extent %', te;
+ sql := 'SELECT count(*), ST_Clip(ST_Union(ST_SnapToGrid(ST_Rescale(ST_Clip(' || quote_ident(col)
+ || ', st_expand($3, greatest($1,$2))),$1, $2, $6), $4, $5, $1, $2)), $3) g FROM ' || tab::text
+ || ' WHERE ST_Intersects(' || quote_ident(col) || ', $3)';
+ --RAISE DEBUG 'SQL: %', sql;
+ FOR rec IN EXECUTE sql USING sfx, sfy, te, ipx, ipy, algo LOOP
+ --RAISE DEBUG '% source tiles intersect target tile %,% with extent %', rec.count, tx, ty, te::box2d;
+ IF rec.g IS NULL THEN
+ RAISE WARNING 'No source tiles cover target tile %,% with extent %',
+ tx, ty, te::box2d;
+ ELSE
+ --RAISE DEBUG 'Tile for extent % has size % x %', te::box2d, st_width(rec.g), st_height(rec.g);
+ RETURN NEXT rec.g;
+ END IF;
+ END LOOP;
+ END LOOP;
+ END LOOP;
+
+ RETURN;
+END;
+$$ LANGUAGE 'plpgsql' STABLE STRICT;
+
+------------------------------------------------------------------------------
+-- ST_CreateOverview
+------------------------------------------------------------------------------
+
+-- Availability: 2.2.0
+CREATE OR REPLACE FUNCTION ST_CreateOverview(tab regclass, col name, factor int, algo text DEFAULT 'NearestNeighbour')
+RETURNS regclass AS $$
+DECLARE
+ sinfo RECORD; -- source info
+ sql TEXT;
+ ttab TEXT;
+BEGIN
+
+ -- 0. Check arguments, we need to ensure:
+ -- a. Source table has a raster column with given name
+ -- b. Source table has a fixed scale (or "factor" would have no meaning)
+ -- c. Source table has a known extent ? (we could actually compute it)
+ -- d. Source table has a fixed tile size (or "factor" would have no meaning?)
+ -- # all of the above can be checked with a query to raster_columns
+ sql := 'SELECT r.r_table_schema sch, r.r_table_name tab, '
+ || 'r.scale_x sfx, r.scale_y sfy, r.blocksize_x tw, '
+ || 'r.blocksize_y th, r.extent ext, r.srid FROM raster_columns r, '
+ || 'pg_class c, pg_namespace n WHERE r.r_table_schema = n.nspname '
+ || 'AND r.r_table_name = c.relname AND r_raster_column = $2 AND '
+ || ' c.relnamespace = n.oid AND c.oid = $1'
+ ;
+ EXECUTE sql INTO sinfo USING tab, col;
+ IF sinfo IS NULL THEN
+ RAISE EXCEPTION '%.% raster column does not exist', tab::text, col;
+ END IF;
+ IF sinfo.sfx IS NULL or sinfo.sfy IS NULL THEN
+ RAISE EXCEPTION 'cannot create overview without scale constraint, try select AddRasterConstraints(''%'', ''%'');', tab::text, col;
+ END IF;
+ IF sinfo.tw IS NULL or sinfo.tw IS NULL THEN
+ RAISE EXCEPTION 'cannot create overview without tilesize constraint, try select AddRasterConstraints(''%'', ''%'');', tab::text, col;
+ END IF;
+ IF sinfo.ext IS NULL THEN
+ RAISE EXCEPTION 'cannot create overview without extent constraint, try select AddRasterConstraints(''%'', ''%'');', tab::text, col;
+ END IF;
+
+ -- TODO: lookup in raster_overviews to see if there's any
+ -- lower-resolution table to start from
+
+ ttab := 'o_' || factor || '_' || sinfo.tab;
+ sql := 'CREATE TABLE ' || quote_ident(sinfo.sch)
+ || '.' || quote_ident(ttab)
+ || ' AS SELECT ST_Retile($1, $2, $3, $4, $5, $6, $7) '
+ || quote_ident(col);
+ EXECUTE sql USING tab, col, sinfo.ext,
+ sinfo.sfx * factor, sinfo.sfy * factor,
+ sinfo.tw, sinfo.th, algo;
+
+ -- TODO: optimize this using knowledge we have about
+ -- the characteristics of the target column ?
+ PERFORM AddRasterConstraints(sinfo.sch, ttab, col);
+
+ PERFORM AddOverviewConstraints(sinfo.sch, ttab, col,
+ sinfo.sch, sinfo.tab, col, factor);
+
+ RETURN ttab;
+END;
+$$ LANGUAGE 'plpgsql' VOLATILE STRICT;
+
-------------------------------------------------------------------
-- Debugging
-------------------------------------------------------------------
--- /dev/null
+SET client_min_messages TO warning;
+CREATE TABLE res1 AS SELECT
+ ST_AddBand(
+ ST_MakeEmptyRaster(10, 10, x, y, 1, -1, 0, 0, 0)
+ , 1, '8BUI', 0, 0
+ ) r
+FROM generate_series(-170, 160, 10) x,
+ generate_series(80, -70, -10) y;
+SELECT addrasterconstraints('res1', 'r');
+
+SELECT ST_CreateOverview('res1', 'r', 2)::text = 'o_2_res1';
+
+SELECT ST_CreateOverview('res1', 'r', 4)::text = 'o_4_res1';
+
+SELECT ST_CreateOverview('res1', 'r', 8)::text = 'o_8_res1';
+
+SELECT ST_CreateOverview('res1', 'r', 16)::text = 'o_16_res1';
+
+SELECT r_table_name tab, r_raster_column c, srid s,
+ scale_x sx, scale_y sy,
+ blocksize_x w, blocksize_y h, same_alignment a,
+ -- regular_blocking (why not regular?)
+ --extent::box2d e,
+ st_covers(extent::box2d, 'BOX(-170 -80,170 80)'::box2d) ec,
+ st_xmin(extent::box2d) = -170 as eix,
+ st_ymax(extent::box2d) = 80 as eiy,
+ (st_xmax(extent::box2d) - 170) <= scale_x as eox,
+ --(st_xmax(extent::box2d) - 170) eoxd,
+ abs(st_ymin(extent::box2d) + 80) <= abs(scale_y) as eoy
+ --,abs(st_ymin(extent::box2d) + 80) eoyd
+ FROM raster_columns
+WHERE r_table_name like '%res1'
+ORDER BY scale_x, r_table_name;
+
+SELECT o_table_name, o_raster_column,
+ r_table_name, r_raster_column, overview_factor
+FROM raster_overviews
+WHERE r_table_name = 'res1'
+ORDER BY overview_factor;
+
+SELECT 'count',
+(SELECT count(*) r1 from res1),
+(SELECT count(*) r2 from o_2_res1),
+(SELECT count(*) r4 from o_4_res1),
+(SELECT count(*) r8 from o_8_res1),
+(SELECT count(*) r16 from o_16_res1)
+;
+
+
+DROP TABLE o_16_res1;
+DROP TABLE o_8_res1;
+DROP TABLE o_4_res1;
+DROP TABLE o_2_res1;
+DROP TABLE res1;
projects / postgis / commitdiff