- From: Fred Andrews <fredandw@live.com>
- Date: Thu, 15 Nov 2012 01:07:30 +0000
- To: Justin Novosad <junov@chromium.org>, "robert@ocallahan.org" <robert@ocallahan.org>
- Cc: whatwg <whatwg@lists.whatwg.org>
The canvas that scripts draw into could be over-sized with the UA down sampling this to fit the target size and taking into account the sub-pixel screen layout when doing so. cheers Fred > Date: Wed, 14 Nov 2012 11:09:49 -0500 > From: junov@chromium.org > To: robert@ocallahan.org > CC: whatwg@lists.whatwg.org > Subject: Re: [whatwg] Enabling LCD Text in 2D canvases. > > On Tue, Nov 13, 2012 at 9:37 PM, Robert O'Callahan <robert@ocallahan.org>wrote: > > > On Mon, Nov 12, 2012 at 2:36 PM, Justin Novosad <junov@chromium.org>wrote: > > > >> Any thoughts? > >> > > > > We'd have to define what happens when you use subpixel antialiasing > > "incorrectly", because we can be pretty sure authors will use it > > incorrectly and expect to get interoperable behavior. > > > > Mozilla supports a "mozOpaque" attribute which makes the canvas buffer > > RGBX (initialized to solid black) and enables subpixel antialiasing for > > most text drawing. That might be enough to address your use-cases. > > > > > On top of that, subpixel antialiasing would have to get turned off if a > rotation or scale (or any transform that breaks pixel alignment), is > applied to the canvas element. > > That is an interesting solution but it is still not 100% safe from the > author's perspective, since there are still several use cases that could > cause artifacts (e.g. applying transforms post rasterization) Even with > this feature, it still requires a lot of care to do everything right 100% > of the time. For example, suppose the page gets zoomed after the canvas > contents were rendered. > Advanced authors will be able to deal with this by triggering a canvas > re-draw, they might even preserve subpixel AA by resizing the canvas and > applying a reciprocal scale to bring the canvas element's effective zoom > back to 1. > > Given how 2d canvas currently works, I don't see any killer solution that > would allow subpixel antialiased text without any caveats. > Are there precedents for exposing features with documented caveats? > (excluding caveats that were discovered after the fact) > > Anyone with brilliant ideas: please speak up! > > Thanks, > > -Justin > > > > Rob > > -- > > Jesus called them together and said, “You know that the rulers of the > > Gentiles lord it over them, and their high officials exercise authority > > over them. Not so with you. Instead, whoever wants to become great among > > you must be your servant, and whoever wants to be first must be your > > slave — just as the Son of Man did not come to be served, but to serve, > > and to give his life as a ransom for many.” [Matthew 20:25-28] > > > >
Received on Thursday, 15 November 2012 01:07:59 UTC