From: Hans Hagen <j.hagen@xs4all.nl>
To: Marco Patzer <lists@homerow.info>
Cc: mailing list for ConTeXt users <ntg-context@ntg.nl>
Subject: Re: Shading and transparency
Date: Thu, 12 Jul 2018 22:59:05 +0200 [thread overview]
Message-ID: <a70c91f3-2627-47f2-19f9-5aef523e71d6@xs4all.nl> (raw)
In-Reply-To: <20180712220830.16a6deff@homerow>
On 7/12/2018 10:08 PM, Marco Patzer wrote:
> On Thu, 12 Jul 2018 11:21:45 +0200
> Hans Hagen <j.hagen@xs4all.nl> wrote:
>
>>> For the old implementation (pre 2016-ish) I had a working solution
>>> because shading to transparent colours just worked (at least in my
>>> case of a simple transparent shade, nothing fancy), but not so any
>>> longer. With the new implementation I couldn't get it working. But
>>> we discussed that at some point in the past. I believe the gist of
>>> it was “shade-to-transparent is gone”.
>>
>> i'm not ssure what shade to transparency means
>
> I mean a shade from a colour (e.g. black) to transparent. For
> instance this used to work pre 2016:
>
> \setupbackgrounds [page] [background=color, backgroundcolor=lightgray]
> \definecolor [trans] [a=multiply, t=1, s=1]
> \starttext
> \startMPcode
> path p; p:=fullsquare xyscaled (5cm, 5cm);
> fill p
> withshading("linear", ulcorner p, llcorner p)
> withfromshadecolor \MPcolor{white}
> withtoshadecolor \MPcolor{trans};
> \stopMPcode
> \stoptext
>
> The shade goes from white to transparent (here lightgray, that's the
> page colour). I assume you have an older context laying around to
> run the example above.
>
>> ... shades can be transparent currently
>
> Yes, but the *whole* shade is made transparent. Currently I don't
> know a way to shade from e.g. black to transparent (no colour). The
> colour involved in the shading can't have transparency, or if they
> do one has to use \MPcoloronly to get rid of the transparency part.
hm, I'm puzzled as a shade doesn't go between colors + transparent but
from one color to another (in the same color space) and transparency is
just a different mechanism
maybe it was some side effect of chosen values / vectors that gave the
combined impression (which is why i want to see the pdf made by context
that you use as reference)
anyway, it helps to be in the same color space
\setupbackgrounds [page] [background=color, backgroundcolor=lightgray]
\starttext
\startuseMPgraphic{test}
graycolor white; white := 1 ;
fill OverlayBox
withshademethod "linear"
withshadedirection shadedup
withshadefactor 1.5
withshadecolors (.85white,white)
% withtransparency (multiplytransparent,.7)
withtransparency (normaltransparent,.7)
\stopuseMPgraphic
\defineoverlay[test][\useMPgraphic{test}]
\framed
[align=middle,background={foreground,test}]
{\samplefile{sapolsky}}
\stoptext
> So the above old syntax roughly translated to the current
> implementation:
>
> \setupbackgrounds [page] [background=color, backgroundcolor=lightgray]
> \definecolor [trans] [a=multiply, t=1, s=1]
> \starttext
> \startMPcode
> path p; p:=fullsquare xyscaled (5cm, 5cm);
> fill p
> withshademethod "linear"
> withshadevector (3, 0)
> %% since "trans" contains transparency, one has to use
> \MPcoloronly withshadecolors (white, \MPcoloronly{trans})
> withtransparency (.5, .5)
> %% withtransparency \MPtransparency{trans}
> ;
> \stopMPcode
> \stoptext
>
>> .. so how did that old file (uncompressed pdf) look like then
>
> Just run the first example with an old context version. The file
> gradient-t from my last mail was created using inkscape as I don't
> want a single project to depend on two different context versions.
you're kidding ... i have no old context on my machine
Hans
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next prev parent reply other threads:[~2018-07-12 20:59 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-11 18:45 Marco Patzer
2018-07-11 21:11 ` Hans Hagen
2018-07-11 21:40 ` Marco Patzer
2018-07-12 9:21 ` Hans Hagen
2018-07-12 20:08 ` Marco Patzer
2018-07-12 20:59 ` Hans Hagen [this message]
2018-07-12 21:53 ` Marco Patzer
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