Problem to reproduce -dissolve

[badabou]

Hello,

I have a serious problem to reproduce the command -dissolve with imagick.
For exemple, can not do that to reproduce under imagick :
composite -dissolve 10 -gravity center over.png bg.png -matte out.png

Do you have an idea ?

Sorry for my English (I’m French).

Thank you for imagemagick program !

[badabou]

I said that using setImageOpacity, transparency original PNG is not retained. Hence my question. Thank you