WITH source AS (
    SELECT rast, geom
    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)
), clipped AS (
    SELECT rast,
        ST_Clip(rast, geom, touched =
> true) AS rast_touched,
        ST_Clip(rast, geom, touched =
> false) AS rast_not_touched
    FROM source
), variants AS (
    SELECT 'original' AS title, ST_Count(rast) AS pixel_count, rast AS rendered
    FROM clipped
    UNION ALL
    SELECT 'all touched', ST_Count(rast_touched), rast_touched
    FROM clipped
    UNION ALL
    SELECT 'default clip', ST_Count(rast_not_touched), rast_not_touched
    FROM clipped
)
SELECT title, pixel_count, ST_AsPNG(rendered) AS image
FROM variants
ORDER BY CASE title
    WHEN 'original' THEN 1
    WHEN 'all touched' THEN 2
    ELSE 3
END;

WITH canvas AS (
    SELECT ST_AddBand(
        ST_AddBand(
            ST_AddBand(
                ST_MakeEmptyRaster(128, 128, 0, 128, 1, -1, 0, 0, 0),
                '8BUI'::text, 0::double precision, 0::double precision
            ),
            '8BUI'::text, 0::double precision, 0::double precision
        ),
        '8BUI'::text, 0::double precision, 0::double precision
    ) AS rast
), source AS (
    SELECT ST_SetValue(
        ST_SetValue(
            ST_SetValue(rast, 1, ST_Buffer('POINT(32 96)'::geometry, 22), 220),
            2, ST_Buffer('LINESTRING(18 20,110 110)'::geometry, 6,
                         'endcap=flat join=bevel'), 210
        ),
        3, ST_Buffer('LINESTRING(10 48,118 48)'::geometry, 7,
                     'endcap=flat'), 180
    ) AS rast,
    ST_Buffer('POINT(64 64)'::geometry, 34) AS clipper
    FROM canvas
), variants AS (
    SELECT 'original RGB' AS title, rast AS rendered FROM source
    UNION ALL
    SELECT 'band 1 cropped', ST_Clip(rast, 1, clipper, true) FROM source
    UNION ALL
    SELECT
        'band 1 only',
        ST_AddBand(
            ST_Clip(rast, 1, clipper, false),
            ARRAY[ST_Band(rast, 2), ST_Band(rast, 3)]
        )
    FROM source
    UNION ALL
    SELECT 'all bands clipped', ST_Clip(rast, clipper, false) FROM source
)
SELECT title, ST_AsPNG(rendered) AS image
FROM variants
ORDER BY CASE title
    WHEN 'original RGB' THEN 1
    WHEN 'band 1 cropped' THEN 2
    WHEN 'band 1 only' THEN 3
    ELSE 4
END;