If you're using canvas, I would look into radial gradient and just animate
its radius. Here's a simple example of a glowing dot —
http://kangax.github.com/jstests/dynamic-glow-effect-with-canvas/ Using
non-linear easing for transition should give it more realism.

-- 
kangax

On Mon, Feb 14, 2011 at 5:45 AM, Mark McDonnell <[email protected]>wrote:

> Thanks Björn
>
> Ps, apologies if this thread has gone off topic, obviously this was
> accidental as I had originally thought this might be possible via Canvas.
>
> Kind regards,
> Mark
>
> 2011/2/14 Björn Söderqvist <[email protected]>
>
>> OK, this is maybe getting a bit off topic since we are moving away
>> from JS-land.
>> You could obviously remove the :focus pseudo-class in the selector to
>> make it show "always".
>> Other than that, check this page out [1] for more examples on how to
>> do animations and pulsation in CSS3 and maybe the concept will be more
>> clear to you. Also it might help to try and play around a bit with the
>> different examples.
>>
>> [1] http://webkit.org/blog/324/css-animation-2/
>>
>> I should note that the crossbrowser support for this is varying as well
>> :-)
>>
>> Good luck.
>> /B.
>>
>> On Mon, Feb 14, 2011 at 11:20 AM, Mark McDonnell <[email protected]>
>> wrote:
>> > Hi Björn,
>> > Sorry, just to be clear that what I need is a pulsating effect (so the
>> dots
>> > have no glow effect, then they start to glow and then the glow slowly
>> fades
>> > out again, then back in/out over and over...)
>> > The article you linked to was fine for animating a glow effect when the
>> user
>> > triggers a focus/blur event on the element, but the dots I need to make
>> glow
>> > on/off needs to be automated - so no user interaction (same as doing a
>> Glow
>> > filter motion tween in Flash basically but with JavaScript).
>> > I don't know if CSS3 transitions can do this (start another animation
>> once
>> > the previous one has finished)? If they can then that's great! and would
>> > love a link to some more information on how to achieve that with CSS3.
>> > Thanks Björn.
>> > Kind regards,
>> > Mark
>> >
>> > 2011/2/14 Björn Söderqvist <[email protected]>
>> >>
>> >> Firstly, yes I suggest CSS3 transitions over canvas.
>> >>
>> >> But then I am not completely sure what you are asking.
>> >> If you are talking about a pulsating effect then it's possible to do
>> >> animations using CSS3 transitions. That's also a part of the example
>> >> in the page I posted. No Javascript needed.
>> >> If you want to be able to toggle the glow on or off, you can have it
>> >> belong to a CSS class which you add/remove with JS.
>> >>
>> >> Cheers,
>> >> Björn
>> >>
>> >> On Mon, Feb 14, 2011 at 10:37 AM, Mark McDonnell <[email protected]
>> >
>> >> wrote:
>> >> > Hi Björn,
>> >> > Thanks for the reply.
>> >> > So just to clarify, that you suggest using CSS3 transitions instead
>> of
>> >> > Canvas.
>> >> > I need these 'glowing dots' to be glowing on/off which I then assume
>> >> > means I
>> >> > would need to use Js to change the relevant CSS3 transition style
>> over
>> >> > time
>> >> > at set intervals - is that possible? I know that Js can change
>> standard
>> >> > CSS
>> >> > properties but I wasn't sure about vendor specific prefixes.
>> >> > Lastly, is this not possible to do with just Canvas?
>> >> > Kind regards,
>> >> > Mark
>> >> > 2011/2/14 Björn Söderqvist <[email protected]>
>> >> >>
>> >> >> Both the DOM and SVG are stylable with CSS3 where you can accomplish
>> >> >> the glow effect:
>> >> >>
>> >> >>
>> http://blog.gesteves.com/post/475773360/css-glow-effects-with-box-shadow
>> >> >>
>> >> >> On Sun, Feb 13, 2011 at 11:00 PM, Mark McDonnell <
>> [email protected]>
>> >> >> wrote:
>> >> >> > Hi,
>> >> >> > I'm completely new to the Canvas API and so my first stop to find
>> out
>> >> >> > more
>> >> >> > about it was here: https://developer.mozilla.org/en/HTML/canvas
>> >> >> > I've gone through some of the basics of drawing objects
>> (rectangles
>> >> >> > and
>> >> >> > circles etc) and am starting to look into integrating images, but
>> >> >> > what I
>> >> >> > want to find out (before wasting too much time on learning Canvas)
>> is
>> >> >> > whether it's good for animating filters such as 'glow' effects?
>> >> >> > Basically I've been asked by my boss to dynamically draw some
>> circles
>> >> >> > on
>> >> >> > top
>> >> >> > of an image and to have these circles show 'glowing' edges. But
>> I've
>> >> >> > no
>> >> >> > idea
>> >> >> > how to achieve this.
>> >> >> > I know there is SVG (with Raphael.js) as a nice abstraction for
>> the
>> >> >> > language
>> >> >> > - and it maybe that SVG is what I should be using - let me know if
>> so
>> >> >> > and
>> >> >> > I'll start investigating that instead.
>> >> >> > Just need some advice on whether Canvas can do what my boss has
>> >> >> > requested,
>> >> >> > and if not, what other JavaScript based solutions (e.g. SVG) are
>> >> >> > there
>> >> >> > to
>> >> >> > achieve this?
>> >> >> > Many thanks.
>> >> >> > Kind regards,
>> >> >> > --
>> >> >> > Mark McDonnell
>> >> >> >
>> >> >> > --
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