How to use GraphicsMagick to negate the alpha channel of a picture

Question

I want to invert a image with transparent background, i.e. from

enter image description here , transparent background

to

enter image description here , transparent "We"

In ImageMagick, we can do this by

convert 1cut.png -channel a -negate +channel 1cut_nega.png

What is the equivalent command in GraphicsMagick?

If I use $ gm convert -channel opacity -negate +channel example/we.png output/we.png, I got a white "We" instead of transparent "We"

Mark Setchell Mark Setchell · Accepted Answer · 2015-06-01T09:52:57

2

votes

I think this is what you want:

gm convert 61I23.png -operator matte negate 1 result.png