Re: Filter Templates

This archive was generated by hypermail 2.4.0 : Monday, 23 January 2023 02:13:56 UTC

Hi Alex,

to make sure I'm not confused.

This is a filter:

<svg version="1.1" xmlns="http://www.w3.org/2000/svg">
 <defs>
   <filter id="srcLoadedOverlay">
     <feImage xlink:href="url(#canvas0)" result="img1" />
     <feImage xlink:href="url(#canvas1)" result="img2" />
     <feImage xlink:href="url(#canvas2)" result="img3" />
     <feBlend in="img1" in2="img2" result="blend1" mode="multiply" />
     <feBlend in="blend1" in2="img3" mode="lighten" />
   </filter>
 </defs>
</svg>

and this would be a property:

<html>
....
<body>
..... <- backdrop
<div style="blend: layer;"> <- group A
  ... <- text, images, etc
  <div style="blend: multiply;"> <- group B
    .. <- text, images, etc
  </div>
</div>

Rik

On Thu, Feb 24, 2011 at 3:53 PM, Alex Danilo <alex@abbra.com> wrote:

> Hi Anthony and all,
>
> --Original Message--:
> >Just adding to what Alex said (see below)...
> >
> >
> >> -----Original Message-----
> >> <snip/>
> >>
> >> Perhaps that should serve as something to look at. This was researched
> >> extensively at the time, and a property works far better than the SVG
> >> filter mechanism when combining a lot of objects for blending.
> >>
> >
> >This is because the background is included twice when using filters to
> perform compositing. This leads to incorrect results - the output tends to
> be darker than expected.
>
> Ignoring side-effects, one of the main advantages of a property
> over a filter is no need for any sort of intermediate bitmap.
>
> The object being blended can be rasterized and alpha blended
> with the correct blend mode directly to the canvas. So the
> performance is significantly higher, especially if you are
> trying to composite lots of graphics on top of live HD video
> where memory bandwidth actually matters.
>
> Alex
>
>