PDFlib Text Extraction Toolkit (TET) Manual

width
(x, y)
beta
fontsize
baseline
fontsize
(x, y)
alpha
width
Fig. 6.3
Glyph metrics for horizontal and vertical writing mode
ed as two separate characters, the uv field of the leading surrogate value will contain
the actual Unicode value (larger than U+FFFF). The uv field of the trailing surrogate
value will be treated as an artificial character, and will have an uv value of 0.
> The type field specifies how the character was created. There are two groups: real and
artificial characters. The group of real characters comprises normal characters (i.e.
the complete result of a single glyph) and characters which start a multi-character
sequence that corresponds to a single glyph (e.g. the first character of a ligature). The
group of artificial characters comprises the continuation of a multi-character sequence
(e.g. the second character of a ligature), the trailing value of a surrogate pair,
and inserted separator characters. For artificial characters the position (x, y) will
specify the endpoint of the most recent real character, the width will be 0, and all
other fields except uv will be those of the most recent real character. The endpoint is
the point (x, y) plus the width added in direction alpha (in horizontal writing mode)
or plus the fontsize in direction -90˚ (in vertical writing mode).
> The unknown field will usually be false (in C and C++: 0), but has a value of true (in C
and C++: 1) if the original glyph could not be mapped to Unicode and has therefore
been replaced with the character specified in the unknownchar option. Using this
field you can distinguish real document content from replaced characters if you
specified a common character as unknownchar, such as a question mark or space.
> The (x, y) fields specify the position of the glyph’s reference point, which is the lower
left corner of the glyph rectangle in horizontal writing mode, and the top center in
vertical writing mode (see Section 6.4, »Support for Chinese, Japanese, and Korean
Text«, page 67 for details on vertical writing mode). For artificial characters, which do
not correspond to any glyph on the page, the point (x, y) specifies the end point of
the most recent real character.
> The width field specifies the width of a glyph according to the corresponding font
metrics and text output parameters, such as character spacing and horizontal scaling.
Since these parameters control the position of the next glyph, the distance between
the reference points of two adjacent glyphs may be different from width. The
6.3 Page and Text Geometry 65