A Graphic is a "graphic symbol" with an inherent shape, color(s), and possibly size. A
"graphic" can be very informally defined as "a little picture" and can be of either a raster
or vector-graphic source type. The term "graphic" is used since the term "symbol" is
similar to "Symbolizer" which is used in a different context in SE.
Open Geospatial Consortium, Johann Sorel (Geomatys), Chris Dillard (SYS Technologies)
Indicates the level of translucency as a floating point number whose value is between 0.0
and 1.0 (inclusive). A value of zero means completely transparent. A value of 1.0 means
completely opaque. If null, the default value is 1.0, totally opaque.
The Size element gives the absolute size of the graphic in uoms encoded as a floating-
point number. The default size for an object is context-dependent. Negative values are
The default size of an image format (such as GIF) is the inherent size of the image. The
default size of a format without an inherent size (such as SVG which are not specially
marked) is defined to be 16 pixels in height and the corresponding aspect in width. If a
size is specified, the height of the graphic will be scaled to that size and the
corresponding aspect will be used for the width. An expected common use case will be
for image graphics to be on the order of 200 pixels in linear size and to be scaled to lower
sizes. On systems that can resample these graphic images "smoothly," the results will be
Returns the expression that will be used to calculate the rotation of the
graphic when it is drawn.
The Rotation element gives the rotation of a graphic in the clockwise direction about its
center point in decimal degrees, encoded as a floating-point number. Negative values
mean counter-clockwise rotation. The default value is 0.0 (no rotation). Note that there is
no connection between source geometry types and rotations; the point used for plotting
has no inherent direction. Also, the point within the graphic about which it is rotated is
format dependent. If a format does not include an inherent rotation point, then the point
of rotation should be the centroid.
The AnchorPoint element of a PointSymbolizer gives the location inside of a Graphic
(or label - see 11.4.4) to use for anchoring the graphic to the main-geometry point. The
coordinates are given as two floating-point numbers in the AnchorPointX and
AnchorPointY elements each with values between 0.0 and 1.0 inclusive. The bounding
box of the graphic/label to be rendered is considered to be in a coordinate space from 0.0
(lower-left corner) to 1.0 (upper-right corner), and the anchor position is specified as a
point in this space. The default point is X=0.5, Y=0.5, which is at the middle height and
middle length of the graphic/label text. A system may choose different anchor points to
AnchorPoint , if null should use a default point X=0.5 Y=0.5
The Displacement gives the X and Y displacements from the "hot-spot" point. This
element may be used to avoid over-plotting of multiple graphic symbols used as part of
the same point symbol. The displacements are in units of measure above and to the right
of the point. The default displacement is X=0, Y=0.
If Displacement is used in conjunction with Size and/or Rotation then the graphic
symbol shall be scaled and/or rotated before it is displaced.s