How - if at all - is it possible to create a fully transparent image with ImageMagick?
The problem: It's always getting a background color, white by default (as per docs)
More specifically, looking for: Not even a single background color stored in the file, so that every viewer that supports PNG will see it as a fully transparent image - just like the input
My commandline is:
magick convert in.png -trim out.png
Standard "transparent" is a zero valued alpha channel over a black background, so rgba(0,0,0,0). If you want to ensure such, then make the background black under the transparent areas. So for example from your command assuming in.png has some transparency:
magick in.png -background black -alpha background -trim +repage out.png
Note that in ImageMagick 7, use magick, not magick convert.