Overview of the page boundaries in Java

Painting QR Code in Java Overview of the page boundaries

Up until now, you ve defined the page size using a Rectangle as the value of one of the five different page boundaries that can exist for a page in a PDF document. You ll learn

more about these boundaries in this section, and you ll work through an example that demonstrates the difference between the two most important page boundaries. Suppose that I wanted to avoid being accused of false modesty. I could try to print a poster measuring one square meter, featuring myself in a Superman outfit. Seriously! The famous commercial artist Dick Kline once made such a drawing. It was sent to me as a gift by Bill Segraves, a long-time iText user. The drawing isn t a raster image. It consists of a sequence of B zier curves that I ve copied into a text file named hero.txt. To do this, you d create a PdfTemplate from such a text file.

public PdfTemplate createTemplate(PdfContentByte content, Rectangle rect, int factor) throws IOException { PdfTemplate template = content.createTemplate( rect.getWidth(), rect.getHeight()); template.concatCTM(factor, 0, 0, factor, 0, 0); FileReader reader = new FileReader(RESOURCE); int c; while ((c = reader.read()) > -1) { template.setLiteral((char)c); } return template; }

As you can see, you can write literal PDF syntax to the direct content using the setLiteral() method. It accepts a char, a float, or a String value. Incorrect use of this method can result in seriously damaged PDF files. Please don t use it before you ve read chapter 14. In the next chapter, we ll return to this example and find a much better way to reuse existing content.

The original drawing is intended to be added on an A4 page, but I want to put it on an A0 document, so I have to scale it with a factor 4 (see ISO-216). I could create a Document with PageSize.A0 like this:

Document document = new Document(PageSize.A0);

So far, you ve been creating documents with only one type of boundary: the media box. The media box defines the boundaries of the physical medium on which the page is to be printed. It may include any extended area surrounding the finished page for bleed, printing marks, or other such purposes. It may also include areas close to the edges of the medium that cannot be marked because of physical limitations of the output device. Content falling outside this boundary may safely be discarded without affecting the meaning of the PDF file. ISO-32000-1:2008, section 14.1.2

The A0 rectangle used in the code line at the end of the previous section is defined like this:

public static final Rectangle A0 = new RectangleReadOnly(2384,3370);

This corresponds to a physical medium measuring 2384 pt x 3370 pt (or 84.10 cm x 118.89 cm, or 33.11 in x 46.81 in).

The values 2384 and 3370 in this constructor match the width and height of the page, but they really form the coordinates of the upper-right corner of a rectangle. The values for the coordinate of the lower-left corner are omitted because they are zero: the lower-left coordinates are (0,0).

When you learned how to add lines, shapes, and text at absolute positions in chapter 3, you assumed that the origin of the coordinate system coincided with the lowerleft corner of the page. This assumption is correct as long as the media box is defined with (0,0) as the coordinate for its lower-left corner, but that s not mandatory. It s perfectly OK for an application to create a media box with a different origin. It might be interesting to have the origin of the coordinate system in the upperleft corner of the page. Or you could place the origin in the middle of a page, so that you can distinguish four quadrants for your drawing operations. That s what I did when I created my Superman poster in PDF.