I have a folder of png files that have transparent backgrounds. I would like to convert them from the command line and maintain the images' transparent backgrounds.

I'd appreciate any help.

Since jpgs don't support transparency so how can I specify the output jpg's background color's hex value? Right now it defaults to #ffffff? I have tried this script, but it gives the output jpgs white backgrounds:

mogrify -quality 100 -format jpg *.png

Update

I created these png files in inkscape. I should mention that my goal in converting these pngs to jpgs is to get rid of jagged edges on circular or angular objects. The pngs currently have jagged edges and I read that converting them to jpgs might solve this problem. However converting via the method outlined in Christian Skjødt's answer gives the images even worse jagged edges. Is there a way that I can convert the pngs to jpg and also use anti-aliasing or maybe another technique to get rid of the jagged edges? Thanks for the help.