Name
ST_PixelWidth — Returns the pixel width in geometric units of the spatial reference system.
Synopsis
double precision ST_PixelWidth(raster rast);
Description
Returns the width of a pixel in geometric units of the spatial reference system. In the common case where there is no skew, the pixel width is just the scale ratio between geometric coordinates and raster pixels.
The following diagram demonstrates the relationship:
Pixel Width: Pixel size in the i direction
Pixel Height: Pixel size in the j direction
Examples: Rasters with no skew
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;
rastwidth | pixwidth | scalex | scaley | skewx | skewy
-----------+----------+--------+--------+-------+----------
10 | 2 | 2 | 3 | 0 | 0
5 | 0.05 | 0.05 | -0.05 | 0 | 0
Examples: Rasters with skew different than 0
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;
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