[cairo] Button Graphic

Gerdus van Zyl gerdusvanzyl at gmail.com
Mon Jan 28 12:42:37 PST 2008

Try using an ellipse shape with clipping set to the button. My
thinking being gradients may not be aliased at the edges?

The blending mode should not have an effect on the aliasing just color
(that effects aliasing), but I may be wrong :-) You can try other
operators to see if it is the problem:

I wish someone could alias the PorterDuff operator types to their
Photoshop names and the bitmap effects (eg. blur), that are in some
branch somewhere, then we could have some real fun with cairo.


On Jan 28, 2008 10:22 PM, Travis Griggs <tgriggs at cincom.com> wrote:
> On Jan 28, 2008, at 11:39 AM, Jeremy Moles wrote:
> > Hello all. :)
> >
> > I'm using Cairo with OpenSceneGraph to create a HUD system, and I'm
> > working on creating a demo which will use Cairo to render a nice,
> > vector
> > button object at any resolution. The first screenshot is my "base"
> > button image, and the second screenshot is my _attempt_ at adding a
> > "glossy overlay" that will be rendered when the mouse is over the
> > button. However, as you can see, the "gloss" is extremely poor, and
> > done
> > incorrectly.
> >
> > My question is: how would you guys achieve this same effect with high
> > quality results? First of all, I'm not entire sure I'm even
> > approaching
> > it properly: I create a radial gradient, set the operator to ATOP and
> > extend to NONE, and fill_preserve() that on top of my existing "base"
> > button. The main visual unsightliness (imo) is the jaggies along the
> > edge of the radial gradient, which I'm guessing are a result of my
> > improper usage of the ATOP operator...
> >
> > Also: do you think it would look better if I just "glossed" the inner
> > part of the button, leaving the outlines unaffected? ANY
> > recommendations
> > are welcome, as I'm coming back to Cairo after a very long hiatus and
> > never really fully learned the essentials of vector graphics in the
> > first place (though I've become quite good at using and wrapping the
> > API :)).
> You might check this out:
> http://www.youtube.com/watch?v=vtcP4TheFxE
> You can do everything easily there with Cairo, excepting the shrink/
> rounded corner part.
> --
> Travis Griggs
> Objologist
> "I choose. Therefore, I Am"
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