PDFlib 8 Windows COM/.NET Tutorial

Instead of creating a path object with individual drawing operations you can extract the
clipping path from an imported image:
image = p.load_image("auto", "image.tif", "clippingpathname={path 1}");
/* create a path object from the image’s clipping path */
path = (int) p.info_image(image, "clippingpath", "");
if (path == -1)
throw new Exception("Error: clipping path not found!");
p.draw_path(path, 0, 0, "stroke");
3.2.4 Templates
Templates in PDF. PDFlib supports a PDF feature with the technical name Form
XObjects. However, since this term conflicts with interactive forms we refer to this feature
as templates. A PDFlib template can be thought of as an off-page buffer into which
text, vector, and image operations are redirected (instead of acting on a regular page).
After the template is finished it can be used much like a raster image, and placed an arbitrary
number of times on arbitrary pages. Like images, templates can be subjected to
geometrical transformations such as scaling or skewing. When a template is used on
multiple pages (or multiply on the same page), the actual PDF operators for constructing
the template are only included once in the PDF file, thereby saving PDF output file
size. Templates suggest themselves for elements which appear repeatedly on several
pages, such as a constant background, a company logo, or graphical elements emitted
by CAD and geographical mapping software. Other typical examples for template usage
include crop and registration marks or custom Asian glyphs.
Using templates with PDFlib. Templates can only be defined outside of a page description,
and can be used within a page description. However, templates may also contain
other templates. Obviously, using a template within its own definition is not possible.
Referring to an already defined template on a page is achieved with the fit_image( )
function just like images are placed on the page (see Section 7.3, »Placing Images and
imported PDF Pages«, page 192). The general template idiom in PDFlib looks as follows:
/* define the template */
template = p.begin_template_ext(template_width, template_height, "");
...place marks on the template using text, vector, and image functions...
p.end_template_ext(0, 0);
...
p.begin_page(page_width, page_height);
/* use the template */
p.fit_image(template, 0.0, 0.0, "");
...more page marking operations...
p.end_page();
...
p.close_image(template);
All text, graphics, and color functions can be used on a template. However, the following
functions must not be used while constructing a template:
> load_image( ): images must be loaded outside of a template definition, but can be
used within a template.
3.2 Page Descriptions 73