Re: A better \definesymbol sought

[Hans Hagen <pragma@wxs.nl>]

On 1/24/2017 4:04 AM, Rik wrote:
> On 2017-01-23 14:09, Rik Kabel wrote:
>> On 2017-01-23 00:06, Alan Braslau wrote:
>> > On Sun, 22 Jan 2017 22:39:53 -0500 Rik Kabel > <context@rik.users.panix.com> wrote: > >> So, how can I make the
>> inner glyph (‘?’ in the example below) >> transparent, so that the
>> background shows through along with >> anything else that lives on a
>> lower layer? I’ve seen a method for >> constructed shapes, but nothing
>> that I can apply to text glyphs. >> Undraw doesn’t do it. > > Undraw
>> is simply draw using the background color. > > Transparency is a
>> MetaFun extension to MetaPost (so part of > ConTeXt). > > draw q
>> withtransparency (1,0.5) ; % (method,transparency) > > Alan
>>
>> Hmmm. That does not work for me (with any of many method and
>> transparency values).  The  ‘?’ is solid black. I do see a message in
>> the log that looks related:
>>
>>     mkiv lua stats  > page group warning: transparencies are used but
>>     no pagecolormodel is set
>>
>> but adding \setcolors[state=start,cmyk=yes] does not change that; both
>> the warning and the solid black glyph remain. Could this be an issue
>> of the PDF viewer? Is it a font issue?
> Okay, I got a clean compile using \definecolor and referencing that in
> the MP page.
>
>     \setupbackgrounds
>       [page]
>       [background=color,backgroundcolor=yellow]
>     \definecolor[Transp][r=1,t=0,a=12]
>     \definefont
>       [DVSrB]
>       [file:DejaVuSerif-Bold.ttf]
>     \startuseMPgraphic{HeartTest 1}
>       picture h,q ;
>       h := "♥" infont "\truefontname{DejaVuSerif-Bold.ttf}" scaled 20 ;
>       q := textext("{\DVSrB ?}") scaled 10 ;
>       q := q shifted - (xpart center q, 12pt) ;
>       draw h withcolor blue ;
>       draw q withtransparency(12,0) ;
>       draw q shifted (72pt,0) withtransparency(12,0) ;
>     \stopuseMPgraphic
>     \startuseMPgraphic{HeartTest 2}
>       picture h,q ;
>       h := "♥" infont "\truefontname{DejaVuSerif-Bold.ttf}" scaled 20 ;
>       q := textext("\color[Transp]{\DVSrB ?}") scaled 10 ;
>       q := q shifted - (xpart center q, 12pt) ;
>       draw h withcolor blue ;
>       draw q ;
>       draw q shifted (72pt,0) ;
>     \stopuseMPgraphic
>     \starttext
>      \useMPgraphic{HeartTest 1}
>      \useMPgraphic{HeartTest 2}
>     \stoptext
>
> Unfortunately, the result is not what I want. The result is that the “?”
> disappears, allowing the color directly behind it to show through. The
> example above shows that it works with \definecolor but not
> withwithtransparency. I have no idea why, and certainly realize it could
> be my error.
>
> What I want is that the background of the page (yellow in this case)
> should show through. That is what is done with fill / reverse / cycle,
> as in:
>
>     \setupbackgrounds
>       [page]
>       [background=color,backgroundcolor=yellow]
>     \startuseMPgraphic{CircleTest}
>       path p,q ;
>       p := fullcircle scaled 2cm ;
>       q := fullcircle scaled 1cm ;
>       fill p -- reverse q -- cycle withcolor blue;
>     \stopuseMPgraphic
>     \starttext
>      \useMPgraphic{CircleTest}
>     \stoptext
>
> where the background color (yellow) comes through the inner circle (path q).
>
> Can this be done with text characters? I suspect that the answer is that
> the glyphs have to be converted to paths and that it will only work when

\setupbackgrounds
   [page]
   [background=color,
    backgroundcolor=yellow]
\starttext
     \startcolor[blue]\starteffect[outer]PQR\stopeffect\stopcolor
\stoptext

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                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
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