RE: Semi-Transparent polygone

From: Valeri Onoutchine <Valeri.Onoutchine_at_cern.ch>
Date: Wed, 13 Jul 2005 12:37:16 +0200

Hi Stanislav,
you can use TImage/TASImage class which suppotrs alpha-blending. Check:
http://root.cern.ch/root/htmldoc/TImage.html#TImage:FillPolygon the second parameter is a filled polygon color in format #aarrggbb where

aa - alpha, aka transparency (from 0 to 255). 255 - is non-transparent 
rr - red
gg - green
bb - blue

in hex format.

For example, to create a blue 50% transparent polygon use #880000ff color

Regards. Valeriy

-----Original Message-----

From:	owner-roottalk_at_pcroot.cern.ch on behalf of Stanislav Nesterov
Sent:	Sat 7/9/2005 10:31 AM
To:	Rene Brun
Cc:	roottalk_at_pcroot.cern.ch
Subject:	Re: [ROOT] Semi-Transparent polygone

Hi Rene,

Thank you for the hint. It is not what I am exactly wanted but it may work in my application.

I hope ROOT will incorporate someday real fill-with-colour transparancy. But I understand that it would require some rework in TVirtualX implementations.

Thank you again and

--
       Best regards,
             Stanislav.

Rene Brun wrote:



> Hi Stanislav,

>

> See this example using fill styles with patterns.

>

> Rene Brun

>

> void trans() {

>    TH1F *h1 = new TH1F("h1","test1",100,-2,2);

>    TF1 f1("f1","gaus",-2,2);

>    f1.SetParameters(1,-0.5,1);

>    h1->FillRandom("f1",10000);

>    TH1F *h2 = new TH1F("h2","test2",100,-2,2);

>    f1.SetParameters(1,0.5,0.3);

>    h2->FillRandom("f1",3200);

>    h1->SetFillStyle(3001);

>    h1->SetFillColor(kRed);

>    h1->Draw();

>    h2->SetFillStyle(3010); //try styles between 3001 and 3025

>    h2->SetFillColor(kBlue);

>    h2->Draw("same");

> }

>

>

> On Fri, 8 Jul 2005, Stanislav Nesterov wrote:

>

>> Hello,

>> I would like to know is there any way to draw semi-transparent filled 

>> area in ROOT? At least in version 4.x?

>>

>> AFAIK, the only one object (TPad) in ROOT can be blended with 

>> underlaying layers. All other graphical objects ignore transparency 

>> fill style in sense of blending colours. Maybe today this is not the 

>> case?

>>

>> -- 

>>      Best regards,

>>         Stanislav.

>>

>

Received on Wed Jul 13 2005 - 12:39:49 MEST