Chapter 5. Graphics
In this chapter, we’ll run through the main ways to build graphics in the content stream of a PDF page. All of the examples are based on the same PDF we created manually in Chapter 2 and processed into valid PDF documents with pdftk in the same fashion. All the examples are included in the online resources.
Looking at Content Streams
A PDF page is made up of one or more content
streams, defined by the
/Contents entry in the page object, together
with a shared set of resources, defined by the
/Resources entry. In all our examples, there
will only be a single content stream. Multiple content streams are
equivalent to a single stream containing their concatenated
Here’s an example page, with no resources and a single content stream:
3 0 obj << /Type /Page /Parent 1 0 R /Resources << >> /MediaBox [ 0 0 792 612 ] /Rotate 0 /Contents [ 2 0 R ] >> endobj
Here’s the associated content stream, consisting of the stream dictionary and the stream data.
2 0 obj << /Length 18 >> Stream dictionary stream 200 150 m 600 450 l S Stream data endstream endobj
We’ll discover what the
S operators do in a moment. The numbers are
measurements in points—a point (or pt) is 1/72 inch.
The result of loading this document into a PDF viewer (after processing
with pdftk as per Chapter 2) is shown in Figure 5-1.
The full manually created file (before processing with pdftk) is shown in Example 5-1. We’re going to be using variations on this file for the rest of this chapter. For the ...