code: public float getAscender() {
         float ascender = 0;
         for (int k = 0; k < line.size(); ++k) {
             PdfChunk ck = (PdfChunk)line.get(k);
             if (ck.isImage())
                 ascender = Math.max(ascender, ck.getImage().getScaledHeight() + ck.getImageOffsetY());
             else {
                 PdfFont font = ck.font();
                 ascender = Math.max(ascender, font.getFont().getFontDescriptor(BaseFont.ASCENT, font.size()));
             }
         }
         return ascender;
     }
docs: Gets the maximum size of the ascender for all the fonts used
  in this line.
  @return maximum size of all the ascenders used in this line