Text and Fonts - PDF Explained - page 76

Showing Text
The Tj operator shows text at the current position. This, in combination with the text
positioning operators we have already seen would suffice. However, for convenience
and brevity, three additional operators ( ' , '' , and TJ ) are provided. These are shortcuts
for common combinations of text-showing and text-positioning. The text showing op-
erators are summarized in Table 6-3 .

Table 6-3. Operators for showing text

Operands Operator Function

string Tj Show string at the current position.

string ' Go to the next line, taking into account the leading and text matrices, and show string at the

new position. The same as using T* followed by Tj .

wordspace ,
charspace ,
string

Set the word spacing to wordspace and the character spacing to charspace . Go to the next line,
taking into account the leading and text matrices, and show string at the new position. The
same the sequence wordspace Tw charspace Tc string ' .

''

array TJ This operator allows a text string to be shown with adjustments for individual glyph positions

(for example, kerning). The array contains strings and numbers, in any combination. String
entries are shown as normal; number entries adjust the text matrix horizontally by subtracting
that amount (expressed in thousandths of a unit of text space).

We will now go through some examples of showing text, using the standard font and
the Latin-1 based PDFDocEncoding for simplicity. As always, these examples can be
found in the online resources.

Character and word spacing
Here is our first example, where we show some lines of text using various operators.
The result is illustrated in Figure 6-1 :
BT
/F0 36 Tf
1 0 0 1 120 350 Tm
50 TL
(Character and Word Spacing) Tj T*
3 Tc
(Character and Word Spacing) Tj T*
10 Tw
(Character and Word Spacing) Tj
ET

In this example we have:
1. Used Tf to select font /F0 at 36 points.
2. Used Tm to set the text position to (120, 350).
3. Used TL to set the leading to 50 points.
4. Shown a string with Tj , and used T* to move to the next line.