The code still contains concepts that were used long before Java 8 in many places. Some of these can or should now be replaced by other constructs.

In many places, System.out and System.err are used to write to the console. This should not be the case, as there have been good logging solutions available for years. SLF4J is already included in the EchoSVG dependencies.

if (cycleMethod == MultipleGradientPaint.NO_CYCLE) {
  if (DEBUG)
    System.out.println("NO_CYCLE");

This code can be improved with an SLF4J.

if (cycleMethod == MultipleGradientPaint.NO_CYCLE) {
  LOGGER.debug("NO_CYCLE");