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Re: [whatwg] Support filters in Canvas

From: Dirk Schulze <dschulze@adobe.com>
Date: Wed, 1 Oct 2014 11:00:02 +0000
To: Mark Callow <callow.mark@artspark.co.jp>
Message-ID: <982BC162-BFAD-42EA-AF1D-CF3669C6582E@adobe.com>
Cc: WHAT Working Group <whatwg@whatwg.org>, Markus Stange <mstange@themasta.com>

On Oct 1, 2014, at 12:28 PM, Mark Callow <callow.mark@artspark.co.jp> wrote:

> 
> On 30/09/2014 02:20, Markus Stange wrote:
>> Hi,
>> 
>> I'd like to revive this discussion.
>> 
>> On Sat, Mar 15, 2014 at 12:03 AM, Dirk Schulze 
>> <dschulze@adobe.com>
>>  wrote:
>> 
>> 
>>> I would suggest a filter attribute that takes a list of filter operations
>>> similar to the CSS Image filter function[1]. Similar to shadows[2], each
>>> drawing operation would be filtered. The API looks like this:
>>> 
>>> partial interface CanvasRenderingContext2D {
>>>     attribute DOMString filter;
>>> }
>>> 
>>> A filter DOMString could looks like: “contrast(50%) blur(3px)”
>>> 
>> 
> What happened to the effort to create CSS filters programmable in GLSL? Wasn't that effort addressing canvas filters too? Programmable filters seem more desirable than a fixed set. Last I heard the CSS filters effort was exploring ways to limit filter operations to those that would not allow, for example, the visited state of links to be determined. I think allowing operations only on same-origin data solves those types of issues for canvas.

CSS Shaders are the programmable GLSL filters you mean. Some browser vendors expressed their strong objection to this feature. We’ll explore the feature at a later time. As you said, there were limitations in CSS Shaders that disallow any direct pixel access. This makes it impossible to use CSS Shaders for many use cases. Most of the short hand filters could not be done with CSS Shaders for instance. However, shaders can still be used in WebGL on content without privacy implications.

Greetings,
Dirk

> 
> Regards
> 
>     -Mark
> 
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Received on Wednesday, 1 October 2014 11:00:28 UTC

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