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Issue metadata

Status: WontFix
Owner: ----
Closed: Jul 30
Cc:
Components:
EstimatedDays: ----
NextAction: 2018-07-30
OS: ----
Pri: 3
Type: Bug



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Chrome renders improperly colors with opacity

Reported by m.parzys...@perfectgym.com, Jul 4

Issue description

Chrome Version       :  67.0.3396.99 64bit
URLs (if applicable) : https://codepen.io/parzychu/pen/PagVxm
Other browsers tested:
  Add OK or FAIL, along with the version, after other browsers where you
have tested this issue:
    Firefox 61.0 64bit: OK 
       Edge 42.17134.1.0 EdgeHTML 17.17134: OK 

What steps will reproduce the problem?
(1) See example codepen on Chrome and Firefox or Edge: https://codepen.io/parzychu/pen/PagVxm

What is the expected result?
White block with opacity around 0.3 and 0.6 on blue'ish gray background should have the same hue but should be lighter than background.


What happens instead?
White block with opacity around 0.3 and 0.6 on blue'ish gray has other hue (green'ish) than background.



 
Screenshot_16.png
7.3 KB View Download
Components: Blink>Paint
Inspecting the on-screen color in a standalone colorpicker utility, I see Firefox uses the exact same values for the 2nd and 3rd box, but in Chrome the 3rd box has each channel value increased by one:

  2nd is rgb(238, 243, 246)
  3rd is rgb(239, 244, 247)

I don't know if Chrome is incorrect or the other browsers, but on a good display with 8 *physical* bit per RGB channel I don't see any difference between Chrome or Firefox. A pronounced difference of the hue in this particular case means the display used to observe the artifact has less than 8 physical bit per channel so there are "cliffs" between two almost identical channel values. And each channel has those cliffs at different places which leads to the nonuniform colorization. This is also known to cause so-called "gradient banding". Most of the LCD displays still have less than 8 bit per channel physically so the authors should be careful when using adjacent colors or opacities.
Labels: Needs-Triage-M67
Cc: phanindra.mandapaka@chromium.org
Labels: Needs-Feedback Triaged-ET
Unable to reproduce the issue on reported chrome version 67.0.3396.99 using Windows 7 & 10 and Mac 10.12.6. Attaching screencast for reference.
Steps: 
---------
1. Launched reported chrome and Firefox
2. Navigated to given URL ""https://codepen.io/parzychu/pen/PagVxm"" on both browsers 
3.  Opened Dev tools and inspected all boxes 
As we are observed that the same rgb values(0.3 and 0.6) and background colors on both firefox and chrome browser.

@Reporter: Could you please review the attached screen-cast and confirm if anything being missed here.

Thanks.!
860218.mp4
1.9 MB View Download
NextAction: 2018-07-30
The NextAction date has arrived: 2018-07-30
Status: WontFix (was: Unconfirmed)
Closing due to a lack of feedback. Re-open if feedback becomes available.

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