How to change the opacity for effects ?

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How to change the opacity for effects ?

Postby WhiteBelt » Tue Jul 06, 2010 6:37 pm

Hello, i am a new Inkscape user on MacOS trying to made a switch from Adobe Fireworks.
Mostly i want to use Inkscape for GUI design and for drawing small icons. Love the Icon preview :-)

Having read a lot of good tutorials on how to archive some effects one thing has puzzled me from the beginning.

I draw a rectangle and apply a "drop shadow" effect using the filter editor as described in this tutorial.
The shadow is too dark, i need to lower the opacity of the effect.

How can i change the opacity of the effects only?

My workaround was to duplicate the layer ( no sublayers in Inkscape , meh) , apply the effect to the duplicate layer and then lower the opacity of the duplicate.
Is there another way to go? Or can the workaround be automatized ( copy layer --> apply effect to duplicate --> lower opacity of duplicate) ?

Thanks for your input :-)

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Joined: Sun Jun 06, 2010 1:48 pm

Re: How to change the opacity for effects ?

Postby vwanweb » Wed Jul 07, 2010 6:53 am

1. You can ducplicate layers in the LAYERS menu >Layers >Duplicate Current Layer (it is not clear in your post if this is what you used to duplicate your layer)
then use the Layer Menu to Lower it below the original creation >Layer >Lower Layer (Shift+Ctrl+PgDn)

2. You can also create sub-layers, create a New Layer (Shift+Ctrl+N), use the pull down menu to set the POSITION "As sublayer to current layer"

1&2. Then you could apply an opacity value to the ENTIRE LAYER (sublayer) using the Layers (Shift+Ctrl+L) docked menu's Opacity Slider/Number Entry (located at the bottom) ... ayers.html

3. In th FILTERS menu there is a Drop Shadow Menu...
>FIlters >Shadows and Glow >Drop Shadow... [Drop Shadow Menu]
The Drop Shadow menu has these options.
> Blur Radius,
> Opacity %
> Horiz. Offset
> Vertical, Offset

4. If you are going to work with UI and Icons, I suggest you read up on cloning as this feature is used in inkscape's shared icon files. There is are various ICON .svg files in the /inkscape/share/icons folder. To be safe copy a file and save it under a different directory and name. I've manipulated the pattern file and they no longer work right so be careful in this SHARE directory. ... lones.html

your choice, Draw Freely!

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Re: How to change the opacity for effects ?

Postby Xav » Wed Jul 07, 2010 5:40 pm

Another alternative would be to insert a "Colour Matrix" filter primitive into your filter chain - just before or after the Offset in this case. So you would end up with the following chain:

1) Gaussian blur, input from Source Alpha
2) Colour Matrix, input from Gaussian Blur
3) Offset, input from Colour Matrix
4) Merge, input 1 from Offset, input 2 from Source Graphic

Source Alpha gives the alpha components of your element as a greyscale image, where opaque parts become black, transparent parts white, and translucent parts are shades of grey. So in the example in the tutorial where text is used, it's just an easy way to get a fully black version of the text, regardless of the actual text colour. That black version is then blurred and offset, before being merged back under the original text.

The trick is to change the opacity of that black version before it gets merged. Unfortunately there's no simple filter which just reduces opacity, but the Matrix mode of the Colour Matrix filter will do the job, albeit with a less than intuitive interface.

Basically the last row in the matrix defines the output alpha (opacity) from the filter. The four default figures means that alpha is constructed from: 0.00 times the red value + 0.00 times the green value + 0.00 times the blue value + 1.00 times the alpha value + a fixed offset of 0.00. So to change just the alpha, alter the 1.00 on the last line to something else; 0.5 for half the opacity, for example.
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Joined: Tue Jul 06, 2010 6:15 pm

Re: How to change the opacity for effects ?

Postby WhiteBelt » Wed Jul 07, 2010 8:12 pm

Thank you for those valuable hints. Should have asked earlier, would have saved me a lot of time. But i book it as learning effect :-)
Most impressive is that there is with clones a function similar to Fireworks symbols.

Thanks again...

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