XnView Software

It works, great !
But what was wrong in my commande line ? I thought the -transpcolor parameter was the appropriate one ...
And also, is the color 255 0 0 pre-defined to be the transparent color pour PNG32 ?
Anyway, thanks a lot for your help.

Too bad no one seems to have the same need ...
I have also tried to split it in two separate taks : jpg -> png a first, then adding the transparency with -transpcolor, but I obtain the same result : my black borders are not transparent.
Regards,
Christian

Hello,

I would like to convert a JPG to PNG, adding borders at the left and right and making them transparent. I am trying to do that with this command :
nconvert -out png -canvas 300 300 top-center -transpcolor 0 0 0 -merge_alpha 9781895526066.jpg

But I only get two black borders, not transparent ...