SECTION 8.8
745
Measurement Properties
TABLE 8.109 Entries in a viewport dictionary
KEY
TYPE
VALUE
Type
name
rectangle
(Optional)
The type of PDF object that this dictionary describes; must be
Viewport
for a viewport dictionary.
(Required)
A rectangle in default user space coordinates specifying the location of
the viewport on the page.
The two coordinate pairs of the rectangle must be specified in normalized form;
that is, lower-left followed by upper-right, relative to the measuring coordinate sys-
tem. This ordering determines the orientation of the measuring coordinate system
(that is, the direction of the positive
x
and
y
axes) in this viewport, which may have
a different rotation from the page.
Note:
The coordinates of this rectangle are independent of the origin of the measuring
coordinate system, specified in the
O
entry (see Table 8.111) of the measurement dic-
tionary specified by
Measure
.
BBox
Name
text string
dictionary
(Optional)
A descriptive text string or title of the viewport, intended for use in a
user interface.
(Optional)
A measure dictionary (see Table 8.110) that specifies the scale and units
that should apply to measurements taken on the contents within the viewport.
Measure
A measure dictionary specifies an alternate coordinate system for a region of a
page. Along with the viewport dictionary, it provides the information needed to
convert coordinates in the page’s coordinate system to coordinates in the measur-
ing coordinate system. The measure dictionary provides information for format-
ting the resulting values into textual form for presentation in a graphical user
interface.
gle type of coordinate system, a
rectilinear
coordinate system, specified by the val-
ue
RL
for the
Subtype
entry, which is defined as one in which the
x
and
y
axes are
perpendicular and have units that increment linearly (to the right and up, respec-
tively). Other subtypes are permitted, providing the flexibility to measure using
other types of coordinate systems.