[whatwg] Enabling LCD Text and antialiasing in canvas

Rik Cabanier cabanier at gmail.com
Wed Apr 3 21:50:42 PDT 2013

On Wed, Apr 3, 2013 at 9:25 PM, Mark Callow <callow.mark at artspark.co.jp>wrote:

>  On 2013/04/04 10:08, Rik Cabanier wrote:
> On Wed, Apr 3, 2013 at 5:21 PM, Gregg Tavares <gman at google.com> <gman at google.com> wrote:
>  O RLY?   So you're saying the following 250pt ampersand is stored as a
> bitmap in the font file?
>  &
>  It's not simply stored as a path that you then scale. In some fonts it
> might be in a completely different format than a path (or it could even be
> a bitmap)
>  As screen pixel densities soar, it is increasingly the case that fonts
> are stored simply as paths that are scaled, especially fonts which have
> thousands of characters.

No, that is not true.
Talk to font vendors; fonts are not just a collection of path segments.
They are also not rendered as paths; instead they should have specific

>  Fonts render different from paths. If your UA doesn't do that, you are
> doing it wrong. :-)
> Line art looks different to the human eye than a line of text. Imagina a
> vertical and a horizontal line rendered with sub-pixel AA; they will look
> very different.
>  Vertical and horizontal lines won't have any aliasing to begin with so
> what are you talking about?

Of course they have aliasing.  Why wouldn't they?

>  Text also has the nice property that it's filled with a solid color.
>  I know little about Canvas2D but I do know that PostScript and SVG both
> support gradients etc. when filling text so your statement is wrong.

I worked on the rendering engine of Illustrator and Acrobat for 11 years.
Subpixel AA is disabled for text that is filled with gradients or images
and reverts to normal rendering. AFAIK there is no postscript
implementation that supports subpixel positioning.

Can you point me to a spec where you can fill text in canvas with a
gradient instead of a solid color?

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