/// <summary>
/// The below method is an example from https://svn.apache.org/viewvc/pdfbox/trunk/examples/src/main/java/org/apache/pdfbox/examples/util/AddWatermarkText.java?revision=1873147&view=markup
/// </summary>
/// <param name="doc"></param>
/// <param name="page"></param>
/// <param name="font"></param>
/// <param name="text"></param>
static void addWatermarkText(PDDocument doc, PDPage page, PDFont font, string text)
{
using (PDPageContentStream cs
= new PDPageContentStream(doc, page, PDPageContentStream.AppendMode.APPEND, true, true))
{
float fontHeight = 100; // arbitrary for short text
float width = page.getMediaBox().getWidth();
float height = page.getMediaBox().getHeight();
float stringWidth = font.getStringWidth(text) / 1000 * fontHeight;
float diagonalLength = (float)System.Math.Sqrt(width * width + height * height);
float angle = (float)System.Math.Atan2(height, width);
float x = (diagonalLength - stringWidth) / 2; // "horizontal" position in rotated world
float y = -fontHeight / 4; // 4 is a trial-and-error thing, this lowers the text a bit
cs.transform(Matrix.getRotateInstance(angle, 0, 0));
cs.setFont(font, fontHeight);
// cs.setRenderingMode(RenderingMode.STROKE) // for "hollow" effect
PDExtendedGraphicsState gs = new PDExtendedGraphicsState();
gs.setNonStrokingAlphaConstant(new Float(0.2f));
gs.setStrokingAlphaConstant(new Float(0.2f));
gs.setBlendMode(BlendMode.MULTIPLY);
gs.setLineWidth(new Float(3f));
cs.setGraphicsStateParameters(gs);
cs.setNonStrokingColor(Color.red);
cs.setStrokingColor(Color.red);
cs.beginText();
cs.newLineAtOffset(x, y);
cs.showText(text);
cs.endText();
}
}