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Re: 15.5 Filter effects region

From: Jon Ferraiolo <jferraio@Adobe.COM>
Date: Thu, 13 Jul 2000 09:35:29 -0700
Message-Id: <200007131632.JAA14401@mail-345.corp.Adobe.COM>
To: Jim Mork <jmork@jasc.com>
Cc: "'www-svg@w3.org'" <www-svg@w3.org>
The x/y/width/height on the 'filter' element in effect represent a clipping
region for the filter effects in the relevant coordinate system. For
example, if filterUnits='userSpaceOnUse', then x/y/width/height represent a
clipping region in the current user coordinate system for the graphics
element that is invoking the filter.

If provided, filterRes indicates exactly how many pixels in X and Y are
used for the intermediate offscreen bitmaps. It thus defines a particular
resolution at which the filters are performed. This ability was deemed
necessary to give authors the ability to ensure consistent results across
different media for the filter effects, which might have different visual
results depending on resolution. If not provided, then the user agent picks
a suitable resolution appropriate to the device.

Does this help?

I'll see what I can do about making the spec less ambiguous in this area.

Jon Ferraiolo
SVG Editor
Adobe Systems Incorporated

At 04:00 PM 7/12/00 -0500, Jim Mork wrote:
>I am cleaning up some coordinate system and view issues as they relate to
>filter effects, and I need some section 15.5 clarifications.
>Regarding Filter effects region attributes, 15.5 states:
>"x, y, width, height... indicate the rectangle for the largest possible
>offscreen buffer..."
>"filterRes... indicates the width/height of the intermediate images in
>I am having trouble reconciling these two statements.  I don't see how these
>values can be independent of each other.  Given the confusion, I am having
>trouble finding the answer to a simple question:
>Are graphics with effects rendered at a standard resolution (i.e.,
>filterRes) and then resampled to fit to the view?  (which seems to be
>implied by the second statement)
>Are the effects to be applied on the graphics after they have been rendered
>at the size they appear in the view?  (which seems to be implied by the
>first statement)
>Thanks in advance,
>James Mork
>Senior Software Engineer
>Jasc Software, Inc.
Received on Thursday, 13 July 2000 12:44:14 UTC

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