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Issue 714428 link

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Issue metadata

Status: Duplicate
Merged: issue 682074
Owner: ----
Closed: May 2017
Cc:
Components:
EstimatedDays: ----
NextAction: ----
OS: Mac
Pri: 2
Type: Bug



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Incorrect text sub-pixel antialiasing on canvas

Reported by jkieb...@esri.com, Apr 23 2017

Issue description

UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3078.0 Safari/537.36

Steps to reproduce the problem:
1. Draw white text on a canvas (external monitor, devicePixelRatio is 1)

What is the expected behavior?
Nicely anti-aliased completely white text

What went wrong?
It looks like subpixel anti-aliasing is kicking in wrongly, or at the wrong resolution. If I force -webkit-font-smoothing: antialiased (see test case) anti-aliasing works correctly. Also, if I forcefully supersample (i.e. assuming a devicePixelRatio of 2 even if it isn't), then I do get correct results.

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 60.0.3078.0  Channel: canary
OS Version: OS X 10.11.6
Flash Version: Shockwave Flash 25.0 r0
 
test.html
832 bytes View Download
Screen Shot 2017-04-23 at 09.00.46.png
106 KB View Download

Comment 1 by jkieb...@esri.com, Apr 23 2017

For clarification, in the screenshot I rendered a white W at 32x32 (up-scaled the canvas so the problem is more apparent, but having canvas at 32x32 will also show the issue pretty clearly). On the right is the same rendering, but with -webkit-font-smoothing: antialiased.
Labels: Needs-Triage-M60
Cc: xidac...@chromium.org kkaluri@chromium.org yosin@chromium.org e...@chromium.org
Labels: -Needs-Triage-M60 M60
Status: Untriaged (was: Unconfirmed)
Bisect Info:
===========
Good build : 52.0.2743.0 ,  Revision Range - 394939
Bad build  : 53.0.2744.0 ,  Revision Range - 395221


After executing the old revision bisect script, it as given all good builds.

The following CL's between good and bad build versions:
=========================================================
https://chromium.googlesource.com/chromium/src/+log/52.0.2743.0..53.0.2744.0?pretty=fuller&n=10000


The following are suspecting CL's :
-----------
Review-Url: https://codereview.chromium.org/1995103002 - eae@
Review-Url: https://codereview.chromium.org/1997563002 - yosin@
Review-Url: https://codereview.chromium.org/1962413002 - xidachen@


CC'ing the concern owners, requesting them to look into this issue and help us to reassign this issue to the right owner.


Note:
=====
Issue is only reproducible in Mac 10.12.4 not on Windows 10 and Ubuntu 14.04

Issue 714428 - Good.png
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Issue 714428 - Bad.png
162 KB View Download

Comment 4 by yosin@chromium.org, Apr 28 2017

Cc: -yosin@chromium.org
My patch[1] isn't related to canvas anti-aliasing.

[1] http://crrev.com/1997563002: Get rid of a redundant function alias positionBeforeNode(), May 2016

Comment 5 by junov@chromium.org, May 1 2017

Mergedinto: 682074
Status: Duplicate (was: Untriaged)
Labels: -M60 M-60

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