[whatwg] Enabling LCD Text in 2D canvases.
junov at chromium.org
Mon Nov 12 14:36:14 PST 2012
Looking at the discussion archives, I saw that there have been proposals in
the past for exposing anti-aliasing related features to the 2D canvas
rendering context. I realize these proposals met significant opposition
each time. Nonetheless, I would like to quickly re-open the discussion
because I feel there is a lot at stake for the web platform. How about a
2d canvas rendering context attribute for controlling text anti-aliasing,
which could be used to enable LCD text filtering?
The main motivation is to make web apps better. For many types of apps,
DOM-based rendering is uncompetitively slow (e.g. rendering a large number
of independently positioned text labels). On the other hand, 2D canvas can
deliver significantly better performance in many cases, but there is a
degradation in visual quality due to the lack of LCD text filtering.
Current browsers don't enable LCD text in 2D canvas to prevent rendering
artifacts. If LCD text were enable-able, authors would have to be mindful
of a number of caveats in order to avoid rendering artifacts. For example,
artifacts could result from certain use cases of canvas compositing,
transforms on the canvas element, canvas-to-canvas copying with drawImage
with a transform applied. These are the same caveats native app developers
must face when using LCD text filtering.
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