- From: Stephen White <senorblanco@chromium.org>
- Date: Tue, 13 Aug 2013 11:51:49 -0400
- To: Rik Cabanier <cabanier@gmail.com>
- Cc: WHAT Working Group <whatwg@whatwg.org>, Glenn Maynard <glenn@zewt.org>, bdahl@mozilla.com, w3c@junglecode.net
On Sat, Aug 10, 2013 at 11:07 PM, Rik Cabanier <cabanier@gmail.com> wrote: > > > On Sat, Aug 10, 2013 at 7:50 AM, Glenn Maynard <glenn@zewt.org> wrote: > >> On Sat, Aug 10, 2013 at 7:42 AM, Stephen White <senorblanco@chromium.org>wrote: >> >>> Chrome (well, Skia actually) uses a "hairline" mode for line widths < 1. >>> It draws a line of width 1, and uses the width to modulate the alpha. I >>> think the idea is to prevent blotchiness/unevenness caused by undersampling >>> or missed coverage (Skia uses 16 samples of AA). >>> >> >> That sounds like it should be fine, since it should give results similar >> to what users would expect from simple coverage antialiasing. >> >> I'm not sure that's what I'm seeing, though. >> http://jsfiddle.net/eZEyH/1/ The 0.001 width stroke is being drawn >> solid black in the pixel-centered (left) case. In the right one, >> horizontally aligned to the edge of a pixel, the stroke disappears. (I >> left it vertically pixel-centered, so the box didn't disappear entirely.) >> The right is what I'd expect to always happen with a lineWidth that thin. >> Similar things happen with thicker widths, the 0.001 just makes it very >> easy to see. >> > > That is clearly a bug. :-) > Yep, seems to be a bug in Skia's raster backend. I've logged it as https://code.google.com/p/skia/issues/detail?id=1505; feel free to add further comments there. Stephen > > >> >> This can become visible during animation, eg. >> http://jsfiddle.net/xSUuB/1/. In Chrome, the line flickers between >> solid black and grey. In Firefox, it's antialiased normally, so it >> consistently appears grey (actually shifting between one pixel of grey and >> two pixels of lighter grey). >> > > Yeah. Chrome seems to flip between no AA and AA which sounds like a bug in > their algorithm. >
Received on Tuesday, 13 August 2013 15:52:14 UTC