Perl Graphics Programming

Portable Document Format (PDF)

If any electronic document format were to herald the onset of the paperless world, PDF would be it. PDF is a file format for creating multi-page documents with graphics, images, and text that are intended to be viewed on a wide variety of platforms. PDFs are designed to be suitable for screen display or high resolution printing.

PDF is a kind of simplification and extension of PostScript. The problem with using PostScript as a portable interchange format is that it is a little too flexible and forgiving. The PDF specification adds a layer of structure that allows for applications that depend on more information than the raw graphical data needed to render a page.^[9] Here’s a rough outline of PDF’s features and improvements on PostScript:

Font management

• Type 1 fonts and TrueType fonts can be embedded in a document, so you don’t have to worry about whether the end user has the correct fonts.

• To save space, you can embed only the subset of glyphs actually used.

• Fourteen standard fonts are guaranteed to be available for use by any PDF viewer; these fonts can be used without being included in the document.

• External fonts may be used. A font descriptor is included for each font in the document, allowing the viewer to make an intelligent substitution if an external font is not available.

Efficient document storage

• JPEG compression is used for images. LZQ and Flate compression algorithms may be applied to textual and graphic objects in the document.

• The drawing instruction ...