code: function(config, mapper) {
      this.path = PATH.relative('.', config.path);
      this.name = config.name;
      this.ext = config.ext.replace(/^\./, '');
  
      this.mapper = mapper;
      this.config = config;
  }
docs: @typedef {Object} SpriteConfig
  @property {String} [out = './sprited']
  @property {String} [name = 'common']
  @property {String} [ext = 'png']
  @property {String} [layout = 'smart']
  @property {String|Number|Number[]} [padding = 1]
  @property {String|Ifexists} [ifexists = 'create']
  
  @typedef {Object} Ifexists
  @property {String} [action = 'create']
  @property {SpriteConfig} [config]
  
  @constructor
  @param {SpriteConfig} config
  @param {Mapper} mapper