Blur is choppy on rotation

[Daniel Hendrycks]

When an object, that has blur is rotated, the blur looks rasterised/pixelised and choppy.

[su_v (suv-lp)]

Please attach the SVG file used for the screenshot.

Most likely the same issue as reported in
Bug #562283 “Adding drop shadow to rotated object issue”
<https://bugs.launchpad.net/inkscape/+bug/562283>

To work around this issue, consider either changing the filter rendering settings in the preferences (slows down Inkscape), or grouping the object, blurring the group, and rotating the object inside the group instead of the group itself.

[Daniel Hendrycks (kondo8)]

@~suv
Your right, it is a duplicate of that. Sorry, feel free to close this.

[Daniel Hendrycks (kondo8)]

"To work around this issue, consider either changing the filter rendering settings in the preferences (slows down Inkscape)" I can't find the preference.

[su_v (suv-lp)]

This works for me in a simple test file mimicking your screenshot:

Inkscape Preferences > Filters > Filter effects quality for display:
  [x] Best quality (slowest)

[Daniel Hendrycks (kondo8)]

Thanks, this doesn't completely solve it (it still looks choppy, just not as much) I hope the original bug is resolved.

[su_v (suv-lp)]

Alternatively, you can test a recent development build snapshot (>= r10326): the new cairo-renderer does not show the same artefacts when rotating e.g. a blurred text (see attached screenshot: 0.48.1 to the left, current development branch to the right, both with default preferences).

[su_v (suv-lp)]

SVG file used for the screenshots.

[su_v (suv-lp)]

Reproduced with Inkscape 0.48.1 and 0.48+devel r10325,
No longer reproduced with latest build from cairo-rendering branch and with Inkscape 0.48+devel >= r10326
on Mac OS X 10.5.8 (i386)

[Daniel Hendrycks (kondo8)]

Reconfirmed fix, Windows 7 x64, using latest Win Build r10414.

[insaner (insaner)]

confirmed using 0.48.2 on linux (fedora 14)

repost of my comments on bug #1058960 (in case its of any help):
 -------

here is how i can reproduce the problem:

-create a circle
-add filter>ABCs>black outline
-duplicate the circle (ctrl + D)
-move one circle to the side and rotate
-marvel at pixelation

heres a couple of interesting observations:

-if you turn the second circle to a path, disable the filter (uncheck the filter from the filter editor checkbox while the circle is selected), rotate a bit again, and then reenable the filter, the filter is now smooth again. rotating again with the filter on will pixelize the filter again, but disabling, rotating and reenabling will again make it smooth..
-if you leave the circle as a circle object, the above method doesnt work.

 ---
when i have a chance ill figure out how to test the dev branch to see if the fix solves it for me. (how come i cant just download a precompiled version of this somewhere? its been a year..)

[su_v (suv-lp)]

> -if you turn the second circle to a path, disable the filter (…)
> -if you leave the circle as a circle object, the above method doesnt work.

To be expected: inkscape shapes like circle, ellipses, stars and polygons always use a preserved transform attribute, whereas regular paths use optimized transforms (with default settings).

[su_v (suv-lp)]

> how come i cant just download a precompiled version of this somewhere?

Inkscape offers a PPA for daily trunk builds:
<https://launchpad.net/~inkscape.dev/+archive/trunk>

[insaner (insaner)]

ah, but thats only for ubuntu.. im on fedora on this machine (the one i use to do my inkscape work) my only option is to build from source right? (ive logged into the irc chat room so as not to spam the bug's comment section)

[insaner (insaner)]

the bug is still there in 11729, but now, instead of being pixelated, the object is rendered blurry after a rotate..

to see the problem use "black outline" filter instead

[su_v (suv-lp)]

> the bug is still there in 11729, but now, instead of being
> pixelated, the object is rendered blurry after a rotate..

Not in my tests if the same file (created with Inkscape 0.48) is used to compare how it is rendered… (current trunk no longer has the same filter effects, and the sub-menu 'ABCs' is gone).

[su_v (suv-lp)]

Test file used to compare rendering between stable and trunk. The squares on the locked layer beneath the filtered circles and paths visualize the FERs (filter effects region) depending on whether the object has a transform attribute or not.

In my tests, trunk both on OS X (builds with cairo 1.10.2 and cairo 1.12.2) as well as Ubuntu (cairo 1.12.2) render the filtered objects which have a preserved transformation that gets applied to the filtered region correctly, whereas current stable with the old renderer does show the known artifacts (pixelation) if using default rendering quality preferences.

[insaner (insaner)]

using suv's file, and 11729 (now showing all the correct menus and icons -- heh.. i only compiled inkscape for the first time yesterday) still shows the rotated circles as a bit blurry.. same thing with my own file that made me first see this bug. ie, the non-rotated path is fine, the duplicated then rotated path is blurry.

by the way, i tried in both the default rendering settings (and restarting inkscape), both set to high quality, and both set to low quality.. and all yielded the blurry results

interestingly, gThumb renders my file fine (with all its fancy filters), renders a modified version of suv's file fine (in which i increased the "outline" to 9 SDs), but renders suv's file a bit oddly, in making the outlines lopsided (slightly thicker at the top left hand corner) for all circles but the 2nd, 6th and 8th..

and it might already be obvious to you guys why, but in case its of any further help, gimp also imports all the files in the way that gThumb renders them (ie, all fine except the lopsided outlines for suv's file)

[su_v (suv-lp)]

<off-topic>
> interestingly, gThumb renders my file fine (…)
> gimp also imports all the files in the way that gThumb renders them

Gimp uses librsvg for rasterizing SVG files - librsvg is not a reference SVG implementation for inkscape (the library is developed with a different purpose and supports a smaller set of SVG features than inkscape). Use a modern browser (with known good support for SVG filter effects) or Squiggle (Batik) as reference.
</off-topic>