PNGEncoderOptions fix (close #979)
PNGEncoderOptions fix (close #979)

openfl/openfl,openfl/openfl,NenadBojkovski/openfl,Gama11/openfl,Gama11/openfl,openfl/openfl,Gama11/openfl,Gama11/openfl,NenadBojkovski/openfl