Here is the extension color alpha replace to replace colors setting alpha.
Two modes for input:
RRGGBB replace all elements whith this color
RRHHBBAA replace all elements whith this color and determinate alpha.
extensions->colors->color and alpha replace
Feedback are welcome.
Extension soon on the inkscape addons page: https://inkscape.org/en/download/addons/

What a nice extension!
Just discovering this.
There were many topics here about the need for making partially transparent objects opaque by replacing their colour's alpha values, and it already existed?

Still sadly running on suse that I can't get to work with root thus cannot put the extension to the right folder.
So just bumping this, it should have gotten more attention.

Hello
I've tried the extension in Windows, and It seems to me that only replace a color for other. Doesn't change the opacity for alpha. Or at least I don't see how it could do that, even the code mention opacity.

I couldn't help much in SUSE. My sugestion is to open a terminal, use sudo or su, move the files, and use them in inkscape.

Used gnomesu nautilus, the system freezed in a minute.
Just started to use linux in a while, have no idea how to prevent such behaviour.

Hello:
- What version of Suse are you using, OpenSuse?
http://en.opensuse.org/Terminal
Please refer to your documentation, or the webpage of the distribution .

- Once you have the terminal open, some actions needs to be done as "Super user" or "admin user". To do that you have to use the words "sudo"or "su". Please, check this in your system. Also, You should have to know your admin password, because when you installed SUSE, it must be asked you for a password. (Sorry for my English)

Post your advance here, if you prefer

Using opensuse 12.3 64bit with gnome 3.6.2 on intelcore i5-3210M cpu.
The gnomesu should run any program with a gui as root from the terminal.
It asks for the password, but then refuses to work once the file manager is open.
Also, inkscape crashed many times on the system, by only holding down Ctrl and scrolling with the mouse, which with windows never happened.
Considering to change to another operating system -tried to install ubuntustudio before but it's installer didn't even run.

Hello:
Just for try:
Open Terminal
then: sudo nautilus

??

There is no log file when inkscape crashes?? Have you seen that your video drivers are correctly installed?

Sudo nautilus gives this message:

No protocol specified

** (nautilus:5336): WARNING **: Could not open X display

(nautilus:5336): Gtk-WARNING **: cannot open display:

There is no backup when inkscape crashes that of a sudden, cannot tell if it is logged somewhere.
Didn't installed anything custom, went with the recommended settings.

Lazur URH wrote:Still sadly running on suse that I can't get to work with root thus cannot put the extension to the right folder.

What's wrong with installing user extensions into the user Inkscape profile? You don't need 'sudo' to install files into '~/.config/inkscape/extensions' …

Now I can't even find that config folder, nor the inkscape folder I knew once.
I remember I tried to add an obj to the /share/extensions/3Dpolyobjects somewhere and nautilus refused to paste it, because it wasn't run as root.
That's why I thought it needed the root mode to install extensions.

Thanks for sharing.

Hello iḿ the user xyzvisual, this is a old nick. I dont get this questions before. Now i suscribe to the tread.
@hulf2012 with this extension, you can: change a colors with a fixed opacity or with diferent opacities (leaving empty the alpha hex value in the color box -last two chars from a full inkscape color definition are related to opacity AA-)