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The TextType enumeration may take the following values:
- Text
- RawText
- Svg
- SvgPlus
- SvgPlus2
Text is in layout order, which may not be the same as reading
order. ABCpdf will make sensible assumptions on how items of text
should be combined, but some situations are ambiguous. The TextType.Text format provides sophisticated text analysis and interpolation for a more human readable output. The TextType.RawText format is faster and simpler and provides a more literal interpretation of the text in the document.
SVG is an XML based format for representing vector graphics.
Because SVG is standard XML, it's easy to parse and gives you the
precise position of each item of text on the page. The way that
ABCpdf constructs the SVG should make it easy to extract any
information you require. ABCpdf currently supports SVG text, paths
and image placeholders.
For example, a simple "Hello World" PDF might produce the
following content:
<?xml version="1.0" standalone="no"?>
<!DOCTYPE
svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg
width="612" height="792" x="0" y="0">
<text x="0" y="76.8"
font-size="96" font-family="Times-Roman" >Hello
World</text>
</svg>
SVG+ and SVG+2 are annotated forms of SVG which include details
of the PDF operators and how they relate to the items of content in
the SVG. They can be very useful if you are trying to deconstruct a
page and determine how objects in the PDF relate to objects in the
SVG. In SVG+, SVG elements appear before the pdf elements for their
generating operators, and the pdf elements for the Do operator on
Form XObjects are not generated. In SVG+2, SVG elements appear after
the pdf elements of their generating operators, and the pdf elements
for the Do operator on Form XObjects are generated.
For example, you could use SVG+ to identify the section of a PDF
stream that relates to a particular word on a page. You could then
replace the text show operator for that word with another one.
Effectively, you'd be performing a low-level Search/Replace on the
PDF document. However, you should note that this would not mean that
your layout would automatically adjust if - for example - you were
to replace a short word with a long one.
There is no official standard for SVG+, but if you are familiar
with the PDF specification, it should be easy enough to
understand.
For example, a simple "Hello World" PDF might produce the
following content:
<?xml version="1.0" standalone="no"?>
<!DOCTYPE
svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg
width="612" height="792" x="0" y="0">
<pdf pdf_Op="q"
pdf_StreamID="5" pdf_StreamOffset="0" pdf_StreamLength="1"
/>
<pdf pdf_Op="BT" pdf_StreamID="5" pdf_StreamOffset="3"
pdf_StreamLength="2" />
<pdf pdf_Op="0 Tr" pdf_StreamID="5"
pdf_StreamOffset="7" pdf_StreamLength="4" />
<pdf
pdf_Op="/Fabc6 96 Tf" pdf_StreamID="5" pdf_StreamOffset="13"
pdf_StreamLength="12" />
<pdf pdf_Op="0 0 0 rg"
pdf_StreamID="5" pdf_StreamOffset="27" pdf_StreamLength="8"
/>
<pdf pdf_Op="1 0 0 1 0 715.2 Tm" pdf_StreamID="5"
pdf_StreamOffset="37" pdf_StreamLength="18" />
<pdf
pdf_Op="0 Ts" pdf_StreamID="5" pdf_StreamOffset="57"
pdf_StreamLength="4" />
<text x="0" y="76.8" font-size="96"
font-family="Times-Roman" pdf_CTM="1 0 0 1 0 0" pdf_TM="1 0 0 1 0
715.2" pdf_Trm="96 0 0 96 0 715.2" pdf_Tf="Fabc6" pdf_Tz="100"
pdf_Ts="0" pdf_w1000="5027" pdf_Op="(Hello World) Tj"
pdf_StreamID="5" pdf_StreamOffset="63" pdf_StreamLength="16"
>Hello World</text>
<pdf />
<pdf pdf_Op="ET"
pdf_StreamID="5" pdf_StreamOffset="81" pdf_StreamLength="2"
/>
<pdf pdf_Op="Q" pdf_StreamID="5" pdf_StreamOffset="85"
pdf_StreamLength="1" />
</svg>
The operators within the PDF stream are detailed in the SVG. For
example, the first 'q' operator is located in Object ID 5 at offset 0
and has a length of 1 byte. The 'Tj' operator which shows "Hello
World" is at offset 63 and has length 16. The Current Transformation
Matrix (CTM), the Text Matrix (TM), and other important PDF state
values are shown.
Unfortunately, the XML specification was designed in such a way that it does not allow all ASCII values to be represented. There are certain ranges of characters that are completely banned, and this is true even if you attempt to use entity references to include them. Given that the PDF specification allows a broader range of values, you need to consider how you represent characters outside the XML range. For the pdf_Op attribute, all such characters are moved into the U+E000 Unicode private use area. So to convert this string to a PDF format string, you just need to coerce any such character to a byte. This is only relevant to the pdf_Op attribute.
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Syntax