Bug 57112 – SVG shadow filter (feGaussianBlur) adds shadow of the bounding box

• Component: SVG
• Status: RESOLVED INVALID

[Yoah Bar-David]

When using an avg shadow filter (feGaussianBlur), a shadow is also added to the bounding box of the path (it shouldn't be there).
In the attached example, the vertical and horizontal shadows are wrong.
Firefox (4) renders this well.

[Yoah Bar-David]

Created attachment 86968 [details]
Simple example to recreate the bug

[Dirk Schulze]

I can't reproduce it. Works here for me. Can you give more informations about the platform and the version of webkit you are using please?

[Dirk Schulze]

Yoah any news? A screenshot would be useful too.

[Yoah Bar-David]

I tested it now again on Chrome 13 (dev) on Windows, and I can recreate the problem. I don't have current access nightly or Safari, so can't test there

[Zoltan Herczeg]

Could you attach a screenshot? This might be a platform specific issue.

[Yoah Bar-David]

Created attachment 95758 [details]
Screenshot on Chrome 13. Notice the shadow is of the bounding box on the right and bottom, it should not be there

[Dirk Schulze]

(In reply to comment #6)
> Created an attachment (id=95758) [details]
> Screenshot on Chrome 13. Notice the shadow is of the bounding box on the right and bottom, it should not be there

Can confirm it with another Skia based browser. Maybe just Skia related? Can someone of the Gtk or Qt guys reproduce it on their systems?

Adding more people that may can test it on other platforms.

[Rob Buis]

Hi Dirk,

(In reply to comment #7)
> (In reply to comment #6)
> > Created an attachment (id=95758) [details] [details]
> > Screenshot on Chrome 13. Notice the shadow is of the bounding box on the right and bottom, it should not be there
> 
> Can confirm it with another Skia based browser. Maybe just Skia related? Can someone of the Gtk or Qt guys reproduce it on their systems?
> 
> Adding more people that may can test it on other platforms.

Looks fine with Safari.
Cheers,

Rob.

[Zoltan Herczeg]

Just for curiousity, what does happen, if you keep only the feGaussianBlur filter, and disable the other two filters (offset and blend)? The issue is still there?

[Yoah Bar-David]

(In reply to comment #9)
> Just for curiousity, what does happen, if you keep only the feGaussianBlur filter, and disable the other two filters (offset and blend)? The issue is still there?

Yes, the issues is still there, the blur is applied to the right and bottom of the bounding box. I'll attach source and screenshot

[Yoah Bar-David]

Created attachment 96046 [details]
Reduced case with just blur

[Yoah Bar-David]

Created attachment 96047 [details]
Screenshot of the reduced case with only blur

[Dirk Schulze]

(In reply to comment #11)
> Created an attachment (id=96046) [details]
> Reduced case with just blur

I have two questions. Could you help me testing please?

First: I'd like to know which color the shadows have, if you use SourceGraphic instead of SourceAlpha.

Second: Do you see the shadowed border on using <filter filterUnits="objectBoundingBox" x="0" y="0" width="100%" height="100%" id="drop-shadow">? You may have to change the values of stdDeviation as well.

(In reply to comment #13)

First: The line and shadow are both red, if SourceGraphic is used instead. Also, the bounding box shadow no longer appears when SourceGraphic is used.

Second:
When I changed the filter to 
<filter filterUnits="objectBoundingBox" x="0%" y="0%" width="100%" height="100%" id="drop-shadow">
		<feGaussianBlur in="SourceAlpha" stdDeviation="3" />
	</filter>
I no longer saw the bounding box shadow. However, the ends of the line were clipped.
I also tried different values for stdDeviation, the only affect this had was to adjust the amount of blur, as expected.

I also tried
<filter filterUnits="objectBoundingBox" x="-10%" y="-10%" width="120%" height="120%" id="drop-shadow">
		<feGaussianBlur in="SourceAlpha" stdDeviation="3" />
	</filter>
This gave the same results as the original bug. (Reduced case with just blur).

[Yuta Kitamura]

I hit the same problem on Linux Chromium.

My observations:
- SourceAlpha sometimes contains the right and bottom borders of the bounding box of the target shape. <feGaussianFilter> is not necessary to reproduce this issue.
- If you replace SourceAlpha with SourceGraphic, the problem goes away.
- This issue depends on the size of the image; if you resize the image (by hitting Ctrl+[+/-] key), the wrong borders may appear or disappear.

[Yuta Kitamura]

Created attachment 115954 [details]
Reduced test case without blur

[Yuta Kitamura]

Created attachment 115955 [details]
Screenshot of "Reduced test case without blur"

[Dirk Schulze]

Chromium only bug