Re: [NTG-context] drawarrow and transparency
On 2-5-2012 17:35, Alan BRASLAU wrote: I have a MetaPost question concerning drawarrow withtransparency (or any other compound object). Is there some clever way to achieve uniform transparency for a compound object? For example, in the minimal example below, how can one obtain a transparent arrow without getting an X-ray vision of the arrowhead? \starttext \startMPpage drawarrow origin--(1cm,0) withtransparency(1,.5) ; drawarrow origin--(0,1cm) withtransparency(1,.5) ; \stopMPpage \stoptext This is a side effect of an arrow being a composed graphic. I experimented a bit with transparency grouping and after several variants I settled to the following approach: \starttext \startMPpage[offset=1mm] drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,2mm) asgroup ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,4mm) asgroup isolated ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,6mm) asgroup knockout ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,8mm) asgroup isolated,knockout ; addbackground withcolor green ; \stopMPpage \stoptext As we have to use xforms (a pitty that this is needed) there is the usual interference and something fishy with clipping is going on. Hans - Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com | www.pragma-pod.nl - ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___
Re: [NTG-context] drawarrow and transparency
On Wed, 2 May 2012 21:42:24 +0200 Marco net...@lavabit.com wrote: On 2012-05-02 Alan BRASLAU alan.bras...@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 ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___
Re: [NTG-context] drawarrow and transparency
On May 3, 2012, at 6:32 AM, Alan BRASLAU wrote: 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 I noticed the same thing. I think original problem is with how an arrow is converted to PDF/Postscript drawing commands and how the color is computed when commands are combined. The only solution I can imagine is to define a new arrow macro that constructs the boundary path of the arrow and fills it (i.e., up one side of the stem, around the arrowhead, and down the other side of the stem). As far as I can tell, MetaPost/Postscript does not have commands that compute the boundary path of the region painted by a sequence of commands. (I think that computing the boundary might be a much harder problem in general than computing which points to paint. A straight arrow would be fairly simple.) Michael This e-mail message (including any attachments) is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this message (including any attachments) is strictly prohibited. If you have received this message in error, please contact the sender by reply e-mail message and destroy all copies of the original message (including attachments). ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___
Re: [NTG-context] drawarrow and transparency
Hi Alan, Am 03.05.2012 12:32, schrieb Alan BRASLAU: On Wed, 2 May 2012 21:42:24 +0200 Marco net...@lavabit.com wrote: On 2012-05-02 Alan BRASLAU alan.bras...@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)) ; isn't 'image()' a fixed graphic? the only difference from normal drawing is, that the stuff is not added to 'currentpicture'. think of it more like a stamp, that is used to create identical copies. anyhow, it's probably better and cleaner to use a macro here... 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 what you want (if i understand you right) is a non-isolated 'knockout group'. see 'PLATE 17'**, page 1147, in the pdf reference 1.7 for an example. currently no grouping (objects are in the same transparency group) is supported in metafun. the only possible way to create such a graphic is to use the tikz module (search for 'transparency group' in the tikz manual). hope that helps, Peter ** the complete graphic is a fake, because all of its parts are opaque, pixel based graphics; not a single vector graphic, no transparency at all! what a joke :-D maybe adobe doesn't trust other (or their own) pdf viewers to show the right result!? ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___
[NTG-context] drawarrow and transparency
I have a MetaPost question concerning drawarrow withtransparency (or any other compound object). Is there some clever way to achieve uniform transparency for a compound object? For example, in the minimal example below, how can one obtain a transparent arrow without getting an X-ray vision of the arrowhead? \starttext \startMPpage drawarrow origin--(1cm,0) withtransparency(1,.5) ; drawarrow origin--(0,1cm) withtransparency(1,.5) ; \stopMPpage \stoptext Alan ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___
Re: [NTG-context] drawarrow and transparency
On 2012-05-02 Alan BRASLAU alan.bras...@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 ___ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://tex.aanhet.net archive : http://foundry.supelec.fr/projects/contextrev/ wiki : http://contextgarden.net ___
