code: @Override
  	public double transform(double value) {
  		double logValue = Math.log(value>0?value:0)/Math.log(base);
  		return logValue;
  	}
docs: Apply log transform.
  @param value
  @return log_b(value)
  @see org.biojava.nbio.structure.gui.util.color.ContinuousColorMapperTransform#transform(double)