From: Alan BRASLAU <alan.braslau@cea.fr>
To: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Re: drawarrow and transparency
Date: Thu, 3 May 2012 12:32:47 +0200 [thread overview]
Message-ID: <20120503123247.7592251f@sole.extra.cea.fr> (raw)
In-Reply-To: <20120502214224.754fa3ab@Zewz>
On Wed, 2 May 2012 21:42:24 +0200
Marco <netuse@lavabit.com> wrote:
> On 2012-05-02 Alan BRASLAU <alan.braslau@cea.fr> wrote:
>
> > For example, in the minimal example below, how can one obtain
> > a transparent arrow without getting an X-ray vision of the
> > arrowhead?
>
> Maybe I'm reinventing the wheel here, but you can write a small
> macro that only draws the lines you want. Here is an idea:
>
> \starttext
> \startMPpage
>
> linecap := squared;
> penscale := .5bp;
> pickup pencircle scaled penscale;
>
> def drawmyarrow expr p = _apth:=p; _myfinarr enddef;
> def _myfinarr text t =
> draw _apth cutafter point (-ahlength+.1penscale) on
> _apth t; fill arrowhead _apth t
> enddef;
>
> drawarrow origin -- (1cm,0) withtransparency(1,.5) ;
> drawarrow origin -- (0,1cm) withtransparency(1,.5) ;
> drawmyarrow (1.5cm,0) -- (2.5cm,0) withtransparency(1,.5) ;
> drawmyarrow (1.5cm,0) -- (1.5cm,1cm) withtransparency(1,.5) ;
>
> \stopMPpage
> \stoptext
>
> The (-ahlength+.1penscale) are of course empiric. You should find
> the correct formula to always have a nice match of line and arrow
> whatever ahlength and ahangle values are in use.
>
> Marco
Yes, this is somewhat reinventing the wheel.
I believe that this is somewhat a bug with transparency under MetaFun.
For I tried the following:
\startMPcode
picture pic ; pic := image(drawarrow origin--(1cm,0)) ;
draw pic withtransparency(1,.5) ;
draw pic rotated 90 withtransparency(1,.5) ;
\stopMPcode
Here, the arrowhead is totally opaque and only the "stem"
has transparency. Something is fishy.
Alan
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next prev parent reply other threads:[~2012-05-03 10:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-02 15:35 Alan BRASLAU
2012-05-02 19:42 ` Marco
2012-05-03 10:32 ` Alan BRASLAU [this message]
2012-05-03 12:47 ` Rogers, Michael K
2012-05-03 14:09 ` Peter Rolf
2012-05-05 9:19 ` Hans Hagen
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