PNG view/thumb/convert confliction

[azsd]

when uncheck "[] compose images with alpha", pngs have alpha line edge or shadow will display black block instead mixed image like in thumb.
but when check this option, when use convert function, the dest pictures gif/psd/bmp have losted the alpha channel in source png.
It's strange three same things works totally different.

I mean, Is there view and thumb take the Read/write options differently?
I'd like to view work as thumb or have read options setup separaty in file convertions.

XnView 1.90 <x>

[xnview]

when uncheck "[] compose images with alpha", pngs have alpha line edge or shadow will display black block instead mixed image like in thumb.
but when check this option, when use convert function, the dest pictures gif/psd/bmp have losted the alpha channel in source png.
It's strange three same things works totally different.

I mean, Is there view and thumb take the Read/write options differently?
I'd like to view work as thumb or have read options setup separaty in file convertions.

Thumb compose always the alpha, view use/convert use the setting