Convert Tiff to PNG but Retain its transparency

[kopox]

hi guys, how to batch convert tiff to png but retain its transparency? because after converted to png, the background transparency disappear.
i can use Image->transparent color, but it will make all same color transparent which i don't want it.
i attach the image sample that i use which has transparent background on it.

any idea?

[Rick]

I can confirm that. In Xnview it did not even show the original as transparent. I loaded it into an editing program and it was visible there.I used Photozoom to convert it and again the transparency was gone

[xnview]

There is no alpha channel in this file