Previous Next
217
SECTION 4.3 Graphics State
Note: The definition of round join was changed in PDF 1.5. In rare cases, the imple-
mentation of the previous specification could produce unexpected results.
Miter Limit
When two line segments meet at a sharp angle and mitered joins have been spec-
ified as the line join style, it is possible for the miter to extend far beyond the
thickness of the line stroking the path. The miter limit imposes a maximum on
the ratio of the miter length to the line width (see Figure 4.7). When the limit is
exceeded, the join is converted from a miter to a bevel.
The ratio of miter length to line width is directly related to the angle ϕ between
the segments in user space by the following formula:
miterLength 1 -
---------------------------- = -----------------
-
ϕ
lineWidth sin ⎛ -- ⎞ -
⎝ 2⎠
For example, a miter limit of 1.414 converts miters to bevels for ϕ less than 90
degrees, a limit of 2.0 converts them for ϕ less than 60 degrees, and a limit of 10.0
converts them for ϕ less than approximately 11.5 degrees.
Miter
length
j
Line width
FIGURE 4.7 Miter length
Line Dash Pattern
The line dash pattern controls the pattern of dashes and gaps used to stroke paths.
It is specified by a dash array and a dash phase. The dash array’s elements are
numbers that specify the lengths of alternating dashes and gaps; the numbers
must be nonnegative and not all zero. The dash phase specifies the distance into
Previous Next