CHAPTER 5
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Text
If the parameter is
true
, all glyphs in the text object are treated together as a single
elementary object; when glyphs overlap, later glyphs overwrite (“knock out”) ear-
lier ones in the area of overlap. This behavior is equivalent to treating the entire
text object as if it were a non-isolated knockout transparency group; see Section
dividually rather than to the implicit transparency group as a whole:
•
Graphics state parameters, including transparency parameters, are inherited
from the context in which the text object appears. They are not saved and re-
stored, nor are the transparency parameters reset at the beginning of the trans-
parency group (as they are when a transparency group XObject is explicitly
invoked). Changes made to graphics state parameters within the text object
persist beyond the end of the text object.
•
After the implicit transparency group for the text object has been completely
evaluated, the group results are composited with the backdrop, using the
Normal
blend mode and alpha and soft mask values of 1.0.
5.3 Text Objects
A PDF
text object
consists of operators that can show text strings, move the text
position, and set text state and certain other parameters. In addition, three pa-
rameters are defined only within a text object and do not persist from one text
object to the next:
•
T
m
, the
text matrix
•
T
lm
, the
text line matrix
•
T
rm
, the
text rendering matrix,
which is actually just an intermediate result that
combines the effects of text state parameters, the text matrix
(T
m
),
and the cur-
rent transformation matrix
A text object begins with the
BT
operator and ends with the
ET
operator, as shown
below and described in Table 5.4.
BT
…
Zero or more text operators or other allowed operators
…
ET