SECTION 4.6
293
Patterns
KEY
TYPE
VALUE
TilingType
integer
(Required)
A code that controls adjustments to the spacing of tiles relative to
the device pixel grid:
1
Constant spacing.
Pattern cells are spaced consistently—that is, by a
multiple of a device pixel. To achieve this, the application may need
to distort the pattern cell slightly by making small adjustments to
XStep
,
YStep
, and the transformation matrix. The amount of distor-
tion does not exceed 1 device pixel.
No distortion.
The pattern cell is not distorted, but the spacing
between pattern cells may vary by as much as 1 device pixel, both
horizontally and vertically, when the pattern is painted. This achieves
the spacing requested by
XStep
and
YStep
on average
but not neces-
sarily for each individual pattern cell.
Constant spacing and faster tiling.
Pattern cells are spaced consistently
as in tiling type 1 but with additional distortion permitted to enable a
more efficient implementation.
2
3
BBox
rectangle
(Required)
An array of four numbers in the pattern coordinate system giving
the coordinates of the left, bottom, right, and top edges, respectively, of the
pattern cell’s bounding box. These boundaries are used to clip the pattern
cell.
(Required)
The desired horizontal spacing between pattern cells, measured in
the pattern coordinate system.
(Required)
The desired vertical spacing between pattern cells, measured in
the pattern coordinate system. Note that
XStep
and
YStep
may differ from the
dimensions of the pattern cell implied by the
BBox
entry. This allows tiling
with irregularly shaped figures.
XStep
and
YStep
may be either positive or
negative but not zero.
(Required)
A resource dictionary containing all of the named resources
required by the pattern’s content stream (see Section 3.7.2, “Resource Dic-
(Optional)
An array of six numbers specifying the pattern matrix (see Section
[ 1 0 0 1 0 0 ]
.
XStep
number
number
YStep
Resources
dictionary
Matrix
array
The pattern dictionary’s
BBox
,
XStep
, and
YStep
values are interpreted in the pat-
tern coordinate system, and the graphics objects in the pattern’s content stream
are defined with respect to that coordinate system. The placement of pattern cells