ST_PixelWidth
이전  11.4. 래스터 접근자(accessor)  다음

제목

ST_PixelWidth — 픽셀 너비를 공간 참조 시스템의 기하 단위로 반환합니다.

요약

double precision ST_PixelWidth(raster rast);

Description

픽셀 너비를 공간 참조 시스템의 기하 단위로 반환합니다. 회전하지 않은 일반적인 경우, 픽셀 너비란 단순히 기하 좌표와 래스터 픽셀의 축척 비율일 뿐입니다.

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).

예시

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;
래스터 출력
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;
래스터 출력
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;
래스터 출력
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