ST_PixelWidth
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名称

ST_PixelWidth — 返回空间参考系统的几何单位的像素宽度。

大纲

double precision ST_PixelWidth(raster rast);

Description

返回空间参考系统的几何单位中像素的宽度。 在没有倾斜的常见情况下，像素宽度只是几何坐标与光栅像素之间的比例。

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).

示例

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;
栅格输出
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;
栅格输出
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;
栅格输出
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