SECTION 4.6
305
Patterns
TABLE 4.28 Entries common to all shading dictionaries
KEY
TYPE
VALUE
ShadingType
integer
(Required)
The shading type:
1
2
3
4
5
6
7
Function-based shading
Axial shading
Radial shading
Free-form Gouraud-shaded triangle mesh
Lattice-form Gouraud-shaded triangle mesh
Coons patch mesh
Tensor-product patch mesh
ColorSpace
name or
array
array
(Required)
The color space in which color values are expressed. This may be
any device, CIE-based, or special color space except a
Pattern
space. See
(Optional)
An array of color components appropriate to the color space,
specifying a single background color value. If present, this color is used, be-
fore any painting operation involving the shading, to fill those portions of the
area to be painted that lie outside the bounds of the shading object. In the
opaque imaging model, the effect is as if the painting operation were
performed twice: first with the background color and then with the shading.
Note:
The background color is applied only when the shading is used as part of
a shading pattern, not when it is painted directly with the
sh
operator.
Background
BBox
rectangle
(Optional)
An array of four numbers giving the left, bottom, right, and top
coordinates, respectively, of the shading’s bounding box. The coordinates are
interpreted in the shading’s target coordinate space. If present, this bounding
box is applied as a temporary clipping boundary when the shading is painted,
in addition to the current clipping path and any other clipping boundaries in
effect at that time.
(Optional)
A flag indicating whether to filter the shading function to prevent
aliasing
artifacts. The shading operators sample shading functions at a rate
determined by the resolution of the output device. Aliasing can occur if the
function is not smooth—that is, if it has a high spatial frequency relative to
the sampling rate. Anti-aliasing can be computationally expensive and is usu-
ally unnecessary, since most shading functions are smooth enough or are
sampled at a high enough frequency to avoid aliasing effects. Anti-aliasing
may not be implemented on some output devices, in which case this flag is
ignored. Default value:
false
.
AntiAlias
boolean