ST_PixelWidth
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Name

ST_PixelWidth — Gibt die Pixelbreite in den Einheiten des Koordinatenreferenzsystems aus.

Übersicht

double precision ST_PixelWidth(raster rast);

Description

Gibt die Pixelbreite in den Einheiten des Koordinatenreferenzsystems aus. Beim üblichen Fall ohne Versatz entspricht die Pixelbreite dem Maßstabsverhältnis zwischen den geometrischen Koordinaten und den Rasterpixel.

The following executable example draws the two pixel basis vectors on the same coordinate frame as a skewed raster footprint. The i direction vector is (scaleX, skewY); the j direction vector is (skewX, scaleY).

Beispiele

Pixel basis vectors and footprint for a raster with non-zero skew.

Code
WITH raster AS (
    SELECT ST_MakeEmptyRaster(
        3, 3, 0, 0,
        2, -3, 1, 0.5,
        0
    ) AS rast
)
SELECT
    ST_ConvexHull(rast) AS footprint,
    ST_MakeLine(
        ST_Point(0, 0),
        ST_Point(ST_ScaleX(rast), ST_SkewY(rast))
    ) AS "i direction (scaleX, skewY)",
    ST_MakeLine(
        ST_Point(0, 0),
        ST_Point(ST_SkewX(rast), ST_ScaleY(rast))
    ) AS "j direction (skewX, scaleY)"
FROM raster;
Ausgabe von Rastern
POLYGON((0 0,6 1.5,9 -7.5,3 -9,0 0)) | LINESTRING(0 0,2 0.5) | LINESTRING(0 0,1 -3)
Figure
Geometry figure for visual-rt-st-pixelwidth-01

Rasters with no skew.

Code
SELECT ST_Width(rast) As rastwidth, ST_PixelWidth(rast) As pixwidth,
ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
ST_SkewY(rast) As skewy
FROM dummy_rast;
Ausgabe von Rastern
rastwidth | pixwidth | scalex | scaley | skewx | skewy
-----------+----------+--------+--------+-------+----------
10 |        2 |      2 |      3 |     0 |        0
 5 |     0.05 |   0.05 |  -0.05 |     0 |        0

Rasters with skew different than 0.

Code
SELECT ST_Width(rast) As rastwidth, ST_PixelWidth(rast) As pixwidth,
ST_ScaleX(rast) As scalex, ST_ScaleY(rast) As scaley, ST_SkewX(rast) As skewx,
ST_SkewY(rast) As skewy
FROM (SELECT ST_SetSkew(rast, 0.5, 0.5) As rast
FROM dummy_rast) As skewed;
Ausgabe von Rastern
rastwidth |     pixwidth      | scalex | scaley | skewx | skewy
-----------+-------------------+--------+--------+-------+----------
10 |  2.06155281280883 |      2 |      3 |   0.5 |      0.5
 5 | 0.502493781056044 |   0.05 |  -0.05 |   0.5 |      0.5