[gradsusr] New features (was Re: Feature suggestion - Add alpha channel / transparency value to 'set rgb')

[Jennifer Adams]

On Jun 28, 2012, at 3:55 PM, Stefan Gofferje wrote:

> On 06/28/2012 08:24 PM, Brian Doty wrote:
>> 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
> 
> That looks great! Do I see it right that there's now also truetype
> support - which means that I can finally have äöüÄÖÜ in the plots? :)
Cairo supports fonts via the freetype and fontconfig libraries, but how many fonts you will be able to use will depend on what's available on your local computer systems. GrADS will have to link dynamically with local copies of cairo -- there is no good way to make cairo completely portable and statically linked.
> 
> I have been experimenting with the new shading algorithms. On country
> scale I don't see much difference in the output but shade2 is about
> double as fast as shaded. Is shade2b supposed to create smoother output?
Shade2b is the same as shade2 before the polygons have been merged are are still all sub-gridbox sized. It is slower that shade2.

> One thing that has been kinda bugging me was that the grid interpolation
> still comes out a bit rough on country scale (Finland, NOAA GFS 0.5°).
You can try drawing a grfill plot underneath a shaded plot -- that will fill out some of the missing data gaps along the edges of a shaded plot.
--Jennifer


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> Stefan Gofferje
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Jennifer M. Adams
IGES/COLA
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jma at cola.iges.org



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