SECTION 4.3
223
Graphics State
KEY
TYPE
DESCRIPTION
AIS
boolean
(Optional; PDF 1.4)
The alpha source flag (“alpha is shape”), specifying
whether the current soft mask and alpha constant are to be interpreted as
shape values (
true
) or opacity values (
false
).
(Optional; PDF 1.4)
The text knockout flag, which determines the behavior of
overlapping glyphs within a text object in the transparent imaging model (see
Section 5.2.7, “Text Knockout”).
TK
boolean
Example 4.1 shows two graphics state parameter dictionaries. In the first, auto-
matic stroke adjustment is turned on, and the dictionary includes a transfer func-
tion that inverts its value,
f
(x)
=
1
x.
In the second, overprint is turned off, and
the dictionary includes a parabolic transfer function,
f
(x)
=
(2x
1)
2
, with a sam-
ple of 21 values. The domain of the transfer function, [ 0.0 1.0 ], is mapped to
[ 0 20 ], and the range of the sample values, [ 0 255 ], is mapped to the range of
the transfer function, [ 0.0 1.0 ].
Example 4.1
10 0 obj
<< /Type /Page
/Parent 5 0 R
/Resources 20 0 R
/Contents 40 0 R
>>
endobj
20 0 obj
<< /ProcSet [ /PDF /Text ]
/Font << /F1 25 0 R >>
/ExtGState << /GS1 30 0 R
/GS2 35 0 R
>>
>>
endobj
30 0 obj
<< /Type /ExtGState
/SA true
/TR 31 0 R
>>
endobj
% Page object
% Resource dictionary for page
% First graphics state parameter dictionary
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