Good Morning i have some image png with alpha channel transparency.
In preview i see the image correct, but when print then image have white backcolor.
can help me ?

I use LL17.

Not all printers support transparency unfortunately. You should either try to avoid it completely (as you also never now if you customer uses a device that supports it) or try different printers and printer drivers. In our office, out of five printers only one does support transparency (that one is a color laser DTP printer).