code: public void setShadingFill(PdfShadingPattern shading) {
          writer.addSimpleShadingPattern(shading);
          PageResources prs = getPageResources();
          PdfName name = prs.addPattern(shading.getPatternName(), shading.getPatternReference());
          content.append(PdfName.PATTERN.getBytes()).append(" cs ").append(name.getBytes()).append(" scn").append_i(separator);
          ColorDetails details = shading.getColorDetails();
          if (details != null)
              prs.addColor(details.getColorName(), details.getIndirectReference());
      }
docs: Sets the shading fill pattern.
  @param shading the shading pattern