static ThresholdMap *GetThresholdMapFile(const char *xml,const char *filename,
  const char *map_id,ExceptionInfo *exception)
{
  char
    *p;

  const char
    *attribute,
    *content;

  double
    value;

  register ssize_t
    i;

  ThresholdMap
    *map;

  XMLTreeInfo
    *description,
    *levels,
    *threshold,
    *thresholds;

  (void) LogMagickEvent(ConfigureEvent,GetMagickModule(),
    "Loading threshold map file \"%s\" ...",filename);
  map=(ThresholdMap *) NULL;
  thresholds=NewXMLTree(xml,exception);
  if (thresholds == (XMLTreeInfo *) NULL)
    return(map);
  for (threshold=GetXMLTreeChild(thresholds,"threshold");
       threshold != (XMLTreeInfo *) NULL;
       threshold=GetNextXMLTreeTag(threshold))
  {
    attribute=GetXMLTreeAttribute(threshold,"map");
    if ((attribute != (char *) NULL) && (LocaleCompare(map_id,attribute) == 0))
      break;
    attribute=GetXMLTreeAttribute(threshold,"alias");
    if ((attribute != (char *) NULL) && (LocaleCompare(map_id,attribute) == 0))
      break;
  }
  if (threshold == (XMLTreeInfo *) NULL)
    {
      thresholds=DestroyXMLTree(thresholds);
      return(map);
    }
  description=GetXMLTreeChild(threshold,"description");
  if (description == (XMLTreeInfo *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingElement", "<description>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      return(map);
    }
  levels=GetXMLTreeChild(threshold,"levels");
  if (levels == (XMLTreeInfo *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingElement", "<levels>, map \"%s\"", map_id);
      thresholds=DestroyXMLTree(thresholds);
      return(map);
    }
  map=(ThresholdMap *) AcquireMagickMemory(sizeof(ThresholdMap));
  if (map == (ThresholdMap *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"UnableToAcquireThresholdMap");
  map->map_id=(char *) NULL;
  map->description=(char *) NULL;
  map->levels=(ssize_t *) NULL;
  attribute=GetXMLTreeAttribute(threshold,"map");
  if (attribute != (char *) NULL)
    map->map_id=ConstantString(attribute);
  content=GetXMLTreeContent(description);
  if (content != (char *) NULL)
    map->description=ConstantString(content);
  attribute=GetXMLTreeAttribute(levels,"width");
  if (attribute == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<levels width>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->width=StringToUnsignedLong(attribute);
  if (map->width == 0)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
       "XmlInvalidAttribute", "<levels width>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  attribute=GetXMLTreeAttribute(levels,"height");
  if (attribute == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<levels height>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->height=StringToUnsignedLong(attribute);
  if (map->height == 0)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlInvalidAttribute", "<levels height>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  attribute=GetXMLTreeAttribute(levels,"divisor");
  if (attribute == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingAttribute", "<levels divisor>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->divisor=(ssize_t) StringToLong(attribute);
  if (map->divisor < 2)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlInvalidAttribute", "<levels divisor>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  content=GetXMLTreeContent(levels);
  if (content == (char *) NULL)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlMissingContent", "<levels>, map \"%s\"",map_id);
      thresholds=DestroyXMLTree(thresholds);
      map=DestroyThresholdMap(map);
      return(map);
    }
  map->levels=(ssize_t *) AcquireQuantumMemory((size_t) map->width,map->height*
    sizeof(*map->levels));
  if (map->levels == (ssize_t *) NULL)
    ThrowFatalException(ResourceLimitFatalError,"UnableToAcquireThresholdMap");
  for (i=0; i < (ssize_t) (map->width*map->height); i++)
  {
    map->levels[i]=(ssize_t) strtol(content,&p,10);
    if (p == content)
      {
        (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
          "XmlInvalidContent", "<level> too few values, map \"%s\"",map_id);
        thresholds=DestroyXMLTree(thresholds);
        map=DestroyThresholdMap(map);
        return(map);
      }
    if ((map->levels[i] < 0) || (map->levels[i] > map->divisor))
      {
        (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
          "XmlInvalidContent", "<level> %.20g out of range, map \"%s\"",
          (double) map->levels[i],map_id);
        thresholds=DestroyXMLTree(thresholds);
        map=DestroyThresholdMap(map);
        return(map);
      }
    content=p;
  }
  value=(double) strtol(content,&p,10);
  (void) value;
  if (p != content)
    {
      (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
        "XmlInvalidContent", "<level> too many values, map \"%s\"",map_id);
     thresholds=DestroyXMLTree(thresholds);
     map=DestroyThresholdMap(map);
     return(map);
   }
  thresholds=DestroyXMLTree(thresholds);
  return(map);
}