Shading and transparency

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Marco Patzer

11 Jul 2018 11 Jul '18

6:45 p.m.

Hi! It's shadings and transparency again. For most things transparency is not required since the background colour (white) can be used instead, to achieve the same effect (thanks Hans for the reimplementation/cleanup a while ago). For one use case I worked around this by including an external file and overlay the external file (see attached example). Background: In the actual documents the transparent overlays overlay images to have the edges fade into the page background (only the centre is of interest). Is there a method that does not require an external file or pre-processing? Using the external file works. Just wondering if there's a better - more integrated - way. Marco

Attachments:

5Z7.mkvi (text/x-tex — 873 bytes)
5Z7.pdf (application/pdf — 11.2 KB)
gradient-t.pdf (application/pdf — 2.4 KB)

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Hans Hagen

11 Jul 11 Jul

9:11 p.m.

...

Hi!

It's shadings and transparency again.

For most things transparency is not required since the background colour (white) can be used instead, to achieve the same effect (thanks Hans for the reimplementation/cleanup a while ago). For one use case I worked around this by including an external file and overlay the external file (see attached example).

Background: In the actual documents the transparent overlays overlay images to have the edges fade into the page background (only the centre is of interest).

Is there a method that does not require an external file or pre-processing? Using the external file works. Just wondering if there's a better - more integrated - way. i guess that with some experimenting you can come close but the external file that you use uses masks (actually we do support masks in external

On 7/11/2018 8:45 PM, Marco Patzer wrote: figures) and multiple shades over something in the page stream, stuff i'd only look into when i have to (in principle one can make all kind of fancy mechanisms but does it pay off ... seldom) Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------

Marco Patzer

9:40 p.m.

On Wed, 11 Jul 2018 23:11:31 +0200 Hans Hagen wrote:

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Is there a method that does not require an external file or pre-processing? Using the external file works. Just wondering if there's a better - more integrated - way. i guess that with some experimenting you can come close but the external file that you use uses masks (actually we do support masks in external figures) and multiple shades over something in the page stream

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”.

...

stuff i'd only look into when i have to (in principle one can make all kind of fancy mechanisms but does it pay off ... seldom)

If there's no easy solution, it's alright. If have a workaround. No need to waste time on exotic features (as long as masks in external figures keep working). Still, if you happen to know a trick to pull that off in ConTeXt, let me know. Marco

Hans Hagen

12 Jul 12 Jul

9:21 a.m.

On 7/11/2018 11:40 PM, Marco Patzer wrote:

...

On Wed, 11 Jul 2018 23:11:31 +0200 Hans Hagen wrote:

...
...
Is there a method that does not require an external file or pre-processing? Using the external file works. Just wondering if there's a better - more integrated - way. i guess that with some experimenting you can come close but the external file that you use uses masks (actually we do support masks in external figures) and multiple shades over something in the page stream

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 ... shades can be transparent currently .. so how did that old file (uncompressed pdf) look like then

...

...
stuff i'd only look into when i have to (in principle one can make all kind of fancy mechanisms but does it pay off ... seldom)

If there's no easy solution, it's alright. If have a workaround. No need to waste time on exotic features (as long as masks in external figures keep working). Still, if you happen to know a trick to pull that off in ConTeXt, let me know.

Marco

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

Marco Patzer

8:08 p.m.

On Thu, 12 Jul 2018 11:21:45 +0200 Hans Hagen 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. 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. Marco

Hans Hagen

8:59 p.m.

On 7/12/2018 10:08 PM, Marco Patzer wrote:

...

On Thu, 12 Jul 2018 11:21:45 +0200 Hans Hagen 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 ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl -----------------------------------------------------------------

Marco Patzer

9:53 p.m.

On Thu, 12 Jul 2018 22:59:05 +0200 Hans Hagen wrote:

...

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)

I just checked some older projects and the older versions. I used a mix between - linear_shade… - withshading("linear"… - withshademethod "linear" … depending on the age of the project. And I fail to find a project using transparent shading where the transparency is done in context. I could not get it working now on the older versions. Maybe you're right and it has never worked the way I thought it had. Sorry for the noise.

...

\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

That's basically shading to the background colour, which gives the impression of transparency. I've been using that. Works most of the time. But it's not the same. See the attached file and compare. I guess I'll keep using the external file overlay 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

Silly me :) Marco

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