[gradsusr] Feature suggestion - Add alpha channel / transparency value to 'set rgb'

[Brian Doty]

The new interface to Cairo fully supports transparency, with a new alpha channel setting with "set rgb" where values range from zero to 255.  Even better, there is support for this feature with all forms of output.  I've tested X windows, image, PDF, and Postscript.  SVG is also supposed to work but I've not tested it yet.  There's also pattern fill (and patterns can be transparent).  This all works really well with the new version of shaded contouring that I implemented a year or so ago (gxout shade2).  Which is one of the reasons for going to all the work to implement a new shaded contouring algorithm -- looking down the road to supporting these new features.

For those interested in the software engineering side of this, I've rewritten the entire back-end interface between the GrADS graphics utilities and the "rendering engine".  It will be possible to link in different rendering engines.  So we will keep the "classic" X windows interface -- for the really good performance -- but it will not support the new features.  And we will have a Cairo interface.  I'm doing this because I suspect we will need an interface to other packages as well (perhaps openGL?)  

Here's an animation I put together showing off the transparency:

http://wx.gmu.edu/dev/pwat3.mov

Beware!  It's 40MB!

...Brian

----- Original Message -----
From: "Stefan Gofferje" <stefan at saakeskus.fi>
To: "GrADS Users Forum" <gradsusr at gradsusr.org>
Sent: Wednesday, June 27, 2012 3:28:26 AM
Subject: Re: [gradsusr] Feature suggestion - Add alpha channel / transparency value to 'set rgb'

On 06/27/2012 04:46 AM, Jennifer Adams wrote:
> Transparent colors will be in the release of GrADS 2.1 that has the
> option to use the cairo library to do the graphics rendering. There's
> still a lot of work to do before the release is ready, I'm sorry I have
> no estimate. Here's a sample of what will be possible. --Jennifer

Will it specifically be possible to define different transparency
levels, so that a "rainbow" could go from 255 255 255 0 (white, opaque)
to 255 255 255 240 (white, very transparent)?

-Stefan


-- 
Suomen Sääkeskus - Hyvä sää on makuasia

Stefan Gofferje
Haukantie 2 B 5
FIN-37600 Valkeakoski
GSM:       +358 (41) 7290730

http://www.saakeskus.fi/
stefan at saakeskus.fi


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