Re: [filter-effects] proposal: currentColor in feColorMatrix

Benjamin

Perhaps I am missing something, but the effect you are after seems
achieveable with SVG filters.  <feFlood> can take currentColor.  For
example:

    <svg width="0" height="0">
        <defs>
            <filter id="filter-inkscale" x="0" y="0" width="100%"
height="100%">
                <!-- invert the image -->
                <feColorMatrix in="SourceGraphic" type="matrix" values="-1
 0  0 0 1
                                                                         0
-1  0 0 1
                                                                         0
 0 -1 0 1
                                                                         0
 0  0 1 0" result="inverted"/>
                <feFlood flood-color="currentColor"/>
                <feBlend mode="multiply" in2="inverted"/>
            </filter>
        </defs>
    </svg>

Which AFAICS gives the desired effect described in the article you linked
to.

Demo here: http://jsfiddle.net/py9q6z98/

If you change the value of color in the CSS for the div, the image color
changes to match the text color.

Paul



On 5 November 2014 19:19, Dirk Schulze <dschulze@adobe.com> wrote:

> Hi Ben,
>
> On Nov 4, 2014, at 7:17 PM, Benjamin Denckla <bdenckla@alum.mit.edu>
> wrote:
>
> > Thanks Dirk, for your response.
> >
> > Indeed "bitonal" was a poor word choice. I'm now using "inkscale"
> instead. See
> http://dencklatronic.blogspot.com/2014/10/more-on-bitonal-inkscale-images.html
> .
> >
> > Indeed inkscale could be described as a gradient map with two color
> stops.
> >
> > Perhaps Greenblatt could provide an example use of gradientmap.js using
> the CSS currentColor variable?
> >
> > If that is possible, that could be used to implement transparent
> inkscale.
> >
> > Opaque inkscale would require the background equivalent of currentColor,
> which, oddly, does not seem to exist.
> >
> > Even if all that could be done, I do not feel inkscale should require
> Javascript, in the long run.
> >
> > For one thing, this would prevent it from being used in the most popular
> ebook format: Kindle. Javascript is not allowed in Kindle books, nor would
> I expect Amazon to allow it anytime soon.
> >
> > For another, admittedly more vague thing, it feels like Javascript
> should be used only as an "escape hatch" if you're doing something weird or
> interactive. Inkscale is certainly not interactive. As to whether it is
> weird, that is of course subjective. But I wonder if there is an analogy
> with transparency. What if web standards were missing transparency, and
> someone proposed a way to implement it in Javascript? That would be a great
> workaround until the new standard was propagated to a reasonable percentage
> of the installed base. But ultimately we would want to see transparency
> available without Javascript.
>
> I first wanted to know if I understand you correctly. A JS prototype can
> help to demonstrate issues. We will discuss adding this feature to the next
> level of Filter Effects.
>
> Allowing currentColor for this kind of feature will have security
> requirements. feColorMatrix would get one of the tainted filter primitives
> and the filter can not be used cross origin. We have this problem with
> feFlood, feDropShadow and other primitives[1] already. I do not see this as
> a problem with that though.
>
> In your blog post you mentioned access to foreground and background color.
> currentColor only can represent one color. How would you access the other
> color? Also, currentColor represents the value of the ‘color’ property on
> an ancestor. ‘color’ is used to style text in HTML and could have unwanted
> affects to text there. A solution could be CSS Custom properties[2] of
> course or the latest approach of "brand color” on WHATWG mailing list.
>
> Greetings,
> Dirk
>
> [1] http://dev.w3.org/fxtf/filters/#security
> [2] http://dev.w3.org/csswg/css-variables/
>
>
>
> >
> > Ben
>
>
>