ST_PixelWidth

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
		

See Also

ST_PixelHeight , ST_ScaleX , ST_ScaleY , ST_SkewX , ST_SkewY