[gdal-dev] Hide OGR_STYLE from PDF attributes

[Even Rouault]

Le lundi 12 novembre 2012 15:57:09, Jukka Rahkonen a écrit :
> Jukka Rahkonen <jukka.rahkonen <at> mmmtike.fi> writes:
> > I wonder also why the the example about using png images as symbols in
> > the document http://www.gdal.org/ogr/drv_pdf.html includes  settings for
> > the symbol color. OGR_STYLE in the example is
> > SYMBOL(c:#000000,id:"a_symbol.png"). Does some of the supported image
> > formats really support changing colors on-the-fly?
> 
> I can tell now that color can be used for adjusting transparency if alpha
> channel is included too. The example it not the best possible because
> SYMBOL(c:#000000,id:"a_symbol.png") means the same as plain
> SYMBOL(id:"a_symbol.png") and resulting symbol will be 50% opaque.

Actually SYMBOL(c:#000000,id:"a_symbol.png") would result in a opaque symbol, 
whereas SYMBOL(id:"a_symbol.png") would use the default alpha for brush, 
that's to say 50%.

> Perhaps the example could be edited a bit:
> Alpha channel value controls the opacity/transparency
> SYMBOL(c:#000000FF,id:"a_symbol.png") makes 100% opaque symbol

I've tried to improve the doc about that in r25219.

> 
> 
> -Jukka-
> 
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