Last Comment Bug 490997 - image scaling produces grey line artifacts at some downscaling percentages
: image scaling produces grey line artifacts at some downscaling percentages
Product: Core
Classification: Components
Component: Graphics (show other bugs)
: 1.9.0 Branch
: x86 Linux
-- normal with 4 votes (vote)
: ---
Assigned To: Nobody; OK to take it and work on it
: Milan Sreckovic [:milan]
Depends on:
  Show dependency treegraph
Reported: 2009-05-01 08:29 PDT by David A Thompson
Modified: 2012-01-13 14:42 PST (History)
13 users (show)
See Also:
Crash Signature:
QA Whiteboard:
Iteration: ---
Points: ---
Has Regression Range: ---
Has STR: ---

first test image (407 bytes, image/jpeg)
2009-05-01 08:48 PDT, David A Thompson
no flags Details
second test image (short3-full.jpeg) (544 bytes, image/jpeg)
2009-05-01 08:49 PDT, David A Thompson
no flags Details
self-contained test page (1.37 KB, application/xhtml+xml)
2009-05-01 09:39 PDT, David A Thompson
no flags Details

Description User image David A Thompson 2009-05-01 08:29:27 PDT
User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/2009042315 Firefox/3.0.10
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/2009042315 Firefox/3.0.10

Image scaling in firefox exhibits line artifacts with certain images at certain scaling values. A screenshot is at

In this example, two images are each rendered at three different width values: 100%, 70%, and 50%. The second pink bar image, with a black smudge in the upper left corner exhibits grey lines at the left and top borders of the image when scaled to 50%. This doesn't seem to be ideal scaling behavior.

What next steps should I take? Stuff I have/haven't tried:
- haven't been able to try this on a windows box so am unable to tell if it's some sort of X windows-related issue
- tried it running firefox remotely on a sparc box and the same lines show up
- the grey lines don't appear when the page is viewed with opera
- tried jpeg, gif, png - same artifact occurs in each case

Reproducible: Always

Steps to Reproduce:
1. test XHTML below
2. test images are at

<h:html xmlns:h="">
  <h:img src="./short2-full.jpeg"
     style="border-color: blue; border-width: thin; border-style: solid;
        padding: 2px;" />    

  <h:img src="./short2-full.jpeg"
     style="border-color: blue; border-width: thin; border-style: solid;
        padding: 2px;" />    

 <h:img src="./short2-full.jpeg"
    style="border-color: blue; border-width: thin; border-style: solid;
           padding: 2px;" />    

 <h:img src="./short3-full.jpeg"
    style="border-color: blue; border-width: thin; border-style: solid;
           padding: 2px;" />    

 <h:img src="./short3-full.jpeg"
    style="border-color: blue; border-width: thin; border-style: solid;
           padding: 2px;" />    

 <h:img src="./short3-full.jpeg"
    style="border-color: blue; border-width: thin; border-style: solid;
           padding: 2px;" />    

Comment 1 User image David A Thompson 2009-05-01 08:45:44 PDT
The last comment at suggests another bug has been filed for (apparently) the same issue.
Comment 2 User image David A Thompson 2009-05-01 08:48:07 PDT
Created attachment 375336 [details]
first test image
Comment 3 User image David A Thompson 2009-05-01 08:49:07 PDT
Created attachment 375337 [details]
second test image (short3-full.jpeg)
Comment 4 User image David A Thompson 2009-05-01 09:39:04 PDT
Created attachment 375343 [details]
self-contained test page

self-contained test page referencing image attachments
Comment 5 User image Sylvain Pasche 2009-05-01 17:25:07 PDT
I don't see these artifacts when opening your testcase here (attachment 375343 [details]) with Firefox 3.0.10 on Ubuntu 9.04 (Mozilla official build). Maybe this could be Xserver/driver related.
Comment 6 User image Sylvain Pasche 2009-05-01 20:46:11 PDT
Could be bug 411831. What is your distribution / Xserver version?
Comment 7 User image David A Thompson 2009-05-02 11:03:05 PDT
Apologies for not providing more detail. This does seem to be X-related -- but the symptom set doesn't precisely match that of 411831.

Debian unstable (sid)

xorg                                 1:7.4+1
xserver-xorg                         1:7.4+1
xserver-xorg-core                    2:1.6.1-1

X claims it's using EXA in the log: EXA: (==) intel(0): Using EXA for acceleration

inconsistent with description of bug 411831:
- setting "XAANoOffscreenPixmaps" doesn't resolve problem (not surprising since EXA is being used...)
- the 'black box' problem (comments 103/107) isn't observed
- the 'invisible image' problem (comment 104) isn't observed

consistent with bug 411831:
- grabbing the image and dragging shows the correct image in the drag window (consistent with comment 99).

Interestingly, the gray line artifacts aren't present when acceleration is turned off (Option "NoAccel"). Perhaps this behavior is limited to the intel video driver (and thus only affects a few users)?
Comment 8 User image Sylvain Pasche 2009-05-02 12:23:59 PDT
Thanks for the detailed information. This issue looks like bug 472472 which has been marked as a duplicate of bug 411831, but this one (and maybe bug 472472) could be something else according to the inconsistent symptoms.

It would also be interesting if you could test with Firefox 3.5 or 3.6 (available at and respectively).

That looks like a Xserver/driver issue so it isn't likely that lots of efforts will be spent fixing this on branch (Firefox 3.0). But if it is still showing on 3.5, then it's a different deal.
Comment 9 User image David A Thompson 2009-05-02 14:06:20 PDT
The symptoms I observe are identical to those described for bug 472472 (e.g., zooming in at or yields images with gray lines at the top and left of the image; has images which are affected as well as images which aren't affected).

The behavior occurs in minefield (Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2a1pre) Gecko/20090502 Minefield/3.6a1pre)

Perhaps bug 472472 is not a duplicate of bug 411831 -- although both seem related to X server acceleration.
Comment 10 User image Micah Gersten 2009-05-21 08:12:51 PDT
Ubuntu bug:
Comment 11 User image Jacques Frechet 2009-06-09 18:07:14 PDT
I have been seeing this behavior in Firefox ever since upgrading Ubuntu from Intrepid to Jaunty, readily reproducible by zooming out or viewing a web site that contains scaled images.  I'm pretty sure I had the same version of Firefox both before and after the upgrade; I believe the change in behavior may have been triggered by a change in video driver configuration, from the "fglrx" video driver to the "radeon" driver; note that I am not using the "intel" video driver like the previous commenter, so this bug does affect more than just "intel" users.  As above, attempting to set XAANoOffscreenPixmaps doesn't help, and results in a message that the option is being ignored, probably because the X server claims to be using EXA and not XAA.  This is a 64-bit system, in case that turns out to matter.

I'd readily switch back to "fglrx" but so far my attempts to do so have resulted in a completely unusable system, for (what I assume are) unrelated reasons.  I will verify that Option "NoAccel" makes the symptoms go away and follow up if it fails to behave as expected, but I fear that's not likely to be a viable long-term workaround for performance reasons.  This rendering glitch is a serious problem for me as I use this machine for web design, among other things.

If anyone has run across any kind of viable workaround for this problem, or has a suggestion of something to try, I'm sure I'm not the only one who would enjoy hearing about it!
Comment 12 User image Sylvain Pasche 2009-06-09 18:20:44 PDT
The first thing would be to try with Firefox 3.5 and see if the problem is gone (firefox-3.5 package in Jaunty, or can be downloaded from

Then checking if the issue is still there with the "NoAccel" option can answer if the issue is in Firefox or your graphic card driver.

If the issue is with your graphic card driver, then Firefox can't do much about it unfortunately (except bypassing XRender but that's not for the immediate future).
Comment 13 User image Jacques Frechet 2009-06-09 19:42:01 PDT
The same problem seems to affect firefox-3.5 as well.

Option "NoAccel" did indeed seem to make the problem go away, but also gave me a warning about "low graphics mode" and reverted my dual-monitor setup to a mirrored configuration.  Which could be expected behavior, for all I know.  Either way, it suggests that the X server configuration is indeed a factor.

I very much doubt this will turn out to be Firefox's fault, though it doesn't seem to me that any number of xorg.conf experiments can prove it isn't  -- Firefox could conceivably be doing something wrong that usually happens to work but occasionally causes problems under complex circumstances.

I'm tempted to try to put together a repro case for this bug that doesn't involve Firefox at all, but I evidently don't have a clear enough idea of how Firefox actually renders images to have succeeded in reproducing the artifact thus far.  I've got a toy program here that pops up a window containing a scaled raster image on a white background (using cairo, which I have a vague idea that Firefox might also use), but of course it renders without any artifacts.  Ah well.
Comment 14 User image Sylvain Pasche 2009-06-10 17:35:05 PDT
Firefox uses Cairo [1] for the rendering, so you could write a small Cairo program that does what Firefox does, so you can reproduce the issue without Firefox.
But the real issue is apparently with your graphic card driver, so you could report the issue to the driver authors. Having a small test program can surely help the driver authors to isolate the issue more quickly than having to run Firefox.
It would be even better to make the testcase use the XRender X11 extension directly, that's what Cairo uses on X11. Here's an example of such a testcase:

Comment 15 User image Y-H 2009-06-29 12:30:31 PDT
Any update on whether this is something Mozilla will be working on? While the issue is apparently hardware/driver related (see above), note that the problem is unique to Gecko; the artifacts don't appear in browsers such as Midori (see bug 497813).
Comment 16 User image Clemens Eisserer 2009-08-01 11:41:33 PDT
does using XAA or NoAccel solve the problem?
most likely a bug in the Intel-Video driver:
Comment 17 User image David A Thompson 2009-08-02 13:30:50 PDT
NoAccel 'solves' the problem (see comment #7, above)
Comment 18 User image Y-H 2009-08-02 16:32:50 PDT
The NoAccel fix doesn't seem to be fixing the problem for me. My xorg.conf file is below. I've tried shutting down and clearing the cache. I've tried Option "NoAccel" "yes", Option "NoAccel", and Option "NoAccel" "true". What am I missing? 

# Xorg configuration created by system-config-display

Section "ServerLayout"
	Identifier     "single head configuration"
	Screen      0  "Screen0" 0 0
	InputDevice    "Keyboard0" "CoreKeyboard"

Section "InputDevice"

# keyboard added by rhpxl
	Identifier  "Keyboard0"
	Driver      "kbd"
	Option	    "XkbModel" "pc105+inet"
	Option	    "XkbLayout" "us"

Section "Monitor"
	Identifier   "Monitor0"
	ModelName    "LCD Panel 1024x768"
	HorizSync    31.5 - 48.0
	VertRefresh  56.0 - 65.0
	Option	    "dpms"

Section "Device"
	Identifier  "Videocard0"
	Driver      "intel"
	Option	    "NoAccel" "true"

Section "Screen"
	Identifier "Screen0"
	Device     "Videocard0"
	Monitor    "Monitor0"
	DefaultDepth     24
	SubSection "Display"
		Viewport   0 0
		Depth     24
Comment 19 User image Andris Zāģeris 2009-08-14 15:56:11 PDT
Seeing this bug with an nvidia card (tested with "nv" and "nvidia" drivers).

Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20090803 Ubuntu/9.04 (jaunty) Shiretoko/3.5.2

How can this be a hardware/driver issue if it seems to be a Gecko specific rounding error?
Comment 20 User image Justus Piater 2009-08-30 05:25:35 PDT
The same problem occurs for HTML5 embedded <video>s.

If any (!) pixel of an image is transparent, then the problem goes away.

Does any of this shed any light on the Gecko vs. Cairo question?
Comment 21 User image Joe Drew (not getting mail) 2009-08-30 19:42:49 PDT
If pixels are transparent, then Cairo won't be able to transform an OVER into a SOURCE, so it might use an entirely different codepath in the X server.
Comment 22 User image Jacques Frechet 2009-11-13 11:34:55 PST
After upgrading Ubuntu from Jaunty to Karmic, I am no longer seeing any of the problems I described in my earlier comments.
Comment 23 User image linuxcentre 2009-11-13 14:35:00 PST
I use karmic as shipped and the problem still exists for me using Intel 945GME chipset on a Dell Mini 10v. Also on Ubuntu 9.10 firefox-3.5-3.5.3+build1+nobinonly-0ubuntu6, xserver-xorg-7.4+3ubuntu7, xserver-xorg-video-intel-2.9.0-1ubuntu2

Also exists on latest Fedora 11 / Firefox 3.5.5 with Nvidia ION chipset using the RPM Fusion NVIDIA binary drivers (Acer Revo, xorg-x11-drv-nvidia-libs-190.42-1.fc11.i586, xorg-x11-server-Xorg-1.6.4-0.1.fc11.i586)
Comment 24 User image David Kudlacek 2010-03-09 05:11:46 PST
Hi there, I am Karmic Koala user. Fact is: Unwanted borders are visible only in localhost produced webpages, uploaded webpage is displayed correctly. My laptop is HP Pavilion 2104EA (GA is Intel 945GME). Opera displays the same web always correctly (from loc and remote server), seems to be FF bug only. Is there some special way FF uses GA driver?
Comment 25 User image Nisha 2010-03-10 15:02:26 PST
Hello, I'm using Karmic Koala as well. The black/gray borders are visible in all images that have been scaled down with CSS or width="" height="". For example the logo on Guardian's website looks like this to me: Opera displays the image without the border. 

Is there a fix available?
Comment 26 User image Bijan 2010-08-09 12:29:09 PDT
I have the exact same issue and using FF 3.6.8 on Ubuntu 10.04 LTS - the Lucid Lynx. The issue is on scaled down images. Its been over a year that we have this problem. Please let us know how to fix this or report to the OS bug report if it is OS related.

Comment 27 User image Grant Galitz 2010-09-27 00:39:02 PDT
See bug report
Should be grouped with similar bugs about artifacts when scaling on any operating system, since these bugs seem to be a symptom of a larger bug.
Comment 28 User image Grant Galitz 2010-09-27 00:50:03 PDT
Comment 29 User image Mardeg 2011-06-03 19:30:09 PDT
Can you retest this please now that bug 468496 is fixed?
Comment 30 User image Jeff Muizelaar [:jrmuizel] 2012-01-13 14:42:41 PST
Seems like this is likely fixed. Reopen if not.

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