code: public void setPatternStroke(PdfPatternPainter p, Color color, float tint) {
          checkWriter();
          if (!p.isStencil())
              throw new RuntimeException("An uncolored pattern was expected.");
          PageResources prs = getPageResources();
          PdfName name = writer.addSimplePattern(p);
          name = prs.addPattern(name, p.getIndirectReference());
          ColorDetails csDetail = writer.addSimplePatternColorspace(color);
          PdfName cName = prs.addColor(csDetail.getColorName(), csDetail.getIndirectReference());
          content.append(cName.getBytes()).append(" CS").append_i(separator);
          outputColorNumbers(color, tint);
          content.append(' ').append(name.getBytes()).append(" SCN").append_i(separator);
      }
docs: Sets the stroke color to an uncolored pattern.
  @param p the pattern
  @param color the color of the pattern
  @param tint the tint if the color is a spot color, ignored otherwise