[R] Bug in PDF device when using transparent graphics

[Arne Brutschy]

Hello,

I think I found a bug when creating graphics on a PDF device using
transparency. I'm using ggplots2 like this:

comp <- ggplot(data, aes(x=Problemsize, y=Fitness)) +
        geom_smooth(fill=alpha("blue", 0.2), aes(colour=factor(Clustersize)), size=2)

Which gives me a curve for each "Clustersize" with a transparent blue
"cloud" around it, indication the standard deviation. Of course, using
windows you cannot see this transparent cloud, but when opening a pdf
containing the plot in Adobe Acrobat all is displayed properly.

But: when printing the resulting pdf, only one of the plotted lines
have a transparent stddev, all the others are solid. At first I though
this is a bug of the printer driver... But when importing the pdf file
to CorelDraw, the result is the same. Only one of the blue stddev
markers has a transparency property, the others are simply solid.

BTW, trying to crop the pdf by using "pdfcrop" on linux results in an
error. After fixing the missing transparency in CorelDraw and
exporting the pdf again, this works as well...

I'm not sure if this is a bug or just an improper pdf spec, as Acrobat
displays the the pdf properly. Has anyone encountered something like
this?

Arne