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      SECTION 5.2                                         Text State Param eters and Operators



5.2.6 Text Rise

      Text rise, Trise , specifies the distance, in unscaled text space units, to move the
      baseline up or down from its default location. Positive values of text rise move the
      baseline up. Adjustments to the baseline are useful for drawing superscripts or
      subscripts. The default location of the baseline can be restored by setting the text
      rise to 0. Figure 5.10 illustrates the effect of the text rise. Text rise always applies
      to the vertical coordinate in text space, regardless of the writing mode.


             (This text is ) Tj
             5 Ts                                                    superscripted
                                                      This text is
             (superscripted) Tj


             (This text is ) Tj
             –5 Ts                                    This text is
                                                                     subscripted
             (subscripted) Tj


             (This ) Tj
             –5 Ts
             (text ) Tj
                                                                    moves
             5 Ts                                     This                  around
                                                             text
             (moves ) Tj
             0 Ts
             (around) Tj


                                      FIGURE 5.10 Text rise


5.2.7 Text Knockout

      The text knockout parameter, Tk (PDF 1.4), is a boolean flag that determines
      what text elements are considered elementary objects for purposes of color com-
      positing in the transparent imaging model. Unlike other text state parameters,
      there is no specific operator for setting this parameter; it can be set only through
      the TK entry in a graphics state parameter dictionary by using the gs operator (see
      Section 4.3.4, “Graphics State Parameter Dictionaries”).

      The text knockout parameter applies only to entire text objects; it may not be set
      between the BT and ET operators delimiting a text object. Its initial value is true. If
      its value is false, each glyph in a text object is treated as a separate elementary ob-
      ject; when glyphs overlap, they composite with one another.

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