private static PDPattern getPattern(COSObject base) {
   Long patternType = base.getIntegerKey(ASAtom.PATTERN_TYPE);
   if (patternType != null) {
     int simplePatternType = patternType.intValue();
     switch (simplePatternType) {
       case PDPattern.TYPE_TILING_PATTERN:
         return new PDTilingPattern(base);
       case PDPattern.TYPE_SHADING_PATTERN:
         return new PDShadingPattern(base);
       default:
         LOGGER.debug("PatternType value is not correct");
         return null;
     }
   } else {
     LOGGER.debug("COSObject doesn't contain PatternType key");
     return null;
   }
 }