Legacy ImageMagick Discussions Archive

This one doesn't work :convert test.png -fuzz 20% -fill none -opaque black test.png
But this one does: convert test.png -fuzz XX% -transparent black result.png

Thank you very much. I finally have what I want.

If I have a png file(which is obtained by converting a jpg files), I want to change the black background color to transparent. So I do the following:
convert test.png -fill xc:none -opaque black -fuzz 20% test.png

However, it seems not working, if I do the following
composite -dissolve 100% test ...

xc:none cannot make the background transparent. This is what I tried.

convert -size 640x640 xc:none -fill green -draw "rectangle 0, 128, 639,256" greenbox.jpg

convert -size 640x640 xc:black -fill blue -draw "rectangle 64,64,576,576" bluebox.jpg

composite -dissolve 100% greenbox.jpg bluebox.jpg ...

In the given link http://www.imagemagick.org/Usage/compose/#dissolve, the dissolve 100% example show two pictures which is what I want.
How can I make the background transient?

Hi,
the following images greenbox.jpg and bluebox.jpg are two boxes of different dimension. I want the greenbox to cover the bluebox. I find the -dissolve,
from http://www.imagemagick.org/Usage/compose/#blend and I want to achieve the similar result as the dissolve 100% effect which is the ...