Descrição

Retorna um raster que é suprimido pela geometria de entrada geom. Se o índice de banda não for especificado, todas as bandas são processadas.

Os rasters resultantes da ST_Clip devem ter o valor nodata designado para as áreas suprimidas, um para cada banda. Se nenhum for promovido e o raster de entrada não tiver nenhum valor nodata definido, os valore nodata do raster resultante são ST_MinPossibleValue(ST_BandPixelType(rast, band)). Quando o número de valor nodata no arranjo é menor qua o número de banda, o último no arranjo é usado para as bandas que sobraram. Se o número de valor nodata for maior que o número de banda, os valores extras serão ignorados. Todas as variantes que aceitam um arranjo de valores nodata também aceitam um valor único, que pode ser designado para cada banda.

If crop is not specified, true is assumed meaning the output raster is cropped to the intersection of the geomand rast extents. If crop is set to false, the new raster gets the same extent as rast. If touched is set to true, then all pixels in the rast that intersect the geometry are selected.

Enhanced: 3.5.0 - touched argument added.

Disponibilidade: 2.0.0

Melhorias: 2.1.0 Reescrito em C

Examples here use Massachusetts aerial data available on MassGIS site MassGIS Aerial Orthos.

Examples: Comparing selecting all touched vs. not all touched

SELECT ST_Count(rast) AS count_pixels_in_orig, ST_Count(rast_touched) AS all_touched_pixels, ST_Count(rast_not_touched) AS default_clip
FROM ST_AsRaster(ST_Letters('R'), scalex =
> 1.0, scaley =
> -1.0) AS r(rast)
    INNER JOIN ST_GeomFromText('LINESTRING(0 1, 5 6, 10 10)') AS g(geom)
 ON ST_Intersects(r.rast,g.geom)
 , ST_Clip(r.rast, g.geom, touched =
> true) AS rast_touched
 , ST_Clip(r.rast, g.geom, touched =
> false) AS rast_not_touched;

 count_pixels_in_orig | all_touched_pixels | default_clip
----------------------+--------------------+--------------
                 2605 |                 16 |           10
(1 row)
 

Examples: 1 band clipping (not touched)

-- Clip the first band of an aerial tile by a 20 meter buffer.
SELECT ST_Clip(rast, 1,
        ST_Buffer(ST_Centroid(ST_Envelope(rast)),20)
    ) from aerials.boston
WHERE rid = 4;
                    

-- Demonstrate effect of crop on final dimensions of raster
-- Note how final extent is clipped to that of the geometry
-- if crop = true
SELECT ST_XMax(ST_Envelope(ST_Clip(rast, 1, clipper, true))) As xmax_w_trim,
    ST_XMax(clipper) As xmax_clipper,
    ST_XMax(ST_Envelope(ST_Clip(rast, 1, clipper, false))) As xmax_wo_trim,
    ST_XMax(ST_Envelope(rast)) As xmax_rast_orig
FROM (SELECT rast, ST_Buffer(ST_Centroid(ST_Envelope(rast)),6) As clipper
    FROM aerials.boston
WHERE rid = 6) As foo;

   xmax_w_trim    |   xmax_clipper   |   xmax_wo_trim   |  xmax_rast_orig
------------------+------------------+------------------+------------------
 230657.436173996 | 230657.436173996 | 230666.436173996 | 230666.436173996
                    

Exemplos: 1 banda suprimindo sem cortes e adiciona de volta outras bandas inalteradas

-- Same example as before, but we need to set crop to false to be able to use ST_AddBand
-- because ST_AddBand requires all bands be the same Width and height
SELECT ST_AddBand(ST_Clip(rast, 1,
        ST_Buffer(ST_Centroid(ST_Envelope(rast)),20),false
    ), ARRAY[ST_Band(rast,2),ST_Band(rast,3)] ) from aerials.boston
WHERE rid = 6;
                    

Exemplos: Suprime todas as bandas

-- Clip all bands of an aerial tile by a 20 meter buffer.
-- Only difference is we don't specify a specific band to clip
-- so all bands are clipped
SELECT ST_Clip(rast,
      ST_Buffer(ST_Centroid(ST_Envelope(rast)), 20),
      false
    ) from aerials.boston
WHERE rid = 4;
                    

Veja também

ST_AddBand, ST_Count, ST_MapAlgebra (callback function version), ST_Intersection