[magick-users] making a semi-transparent image more transparent

[Korny Sietsma]

Hi,
I'm trying to make an image that has a solid area, and a semi-opaque
area, and a transparent area, somewhat more transparent.

(The particular example is a rounded rectangle, which is solid, with a
shadow behind it created with the "shadow()" function)

How do I make the whole image 75% of the original opacity, so the
rounded rectangle is transparent, but without messing up the
completely transparent parts of the image?

I tried setting "image.opacity = Magick::MaxRGB * 0.75" - however this
seems to set all the transparent parts of the image to 75% opacity as
well.

I'm sure I could work out a way to do this by composing the image over
another one - but that seems overly complex.  Surely there's a simple
way to do this?

- Korny
-- 
Kornelis Sietsma korny at my surname dot com