R help - Aug 2009 - Transparency and trellis device

Dear R-users,

I am trying to produce trellis (png, or jpeg) graphs with transparent
background, but I cannot manage to make that happen. I tried to play around with
themes but to no avail. Any advise on the following example will be greatly
appreciated:

Thank you

Sebastien

####
library(lattice)

df <- data.frame(a=rep(1:4,4), b=rep(1:4,4), c=rep(1:4,each=4))

settings <- standard.theme()
settings <- modifyList(settings,
                       list(background=list(alpha=1,
                                            col="transparent")))
str(settings)

trellis.device(png,
               file="test.png",
               theme=settings)

myplot<-xyplot(b~a|c, data=df)

print(myplot)

dev.off()

####

Just replying to bring back some attention on my post, which might have slept
through on Saturday.

Thank you for your help.


----- Mail Original -----
De: pomchip at free.fr
?: r-help at stat.math.ethz.ch
Envoy?: Samedi 1 Ao?t 2009 15h48:24 GMT -05:00 USA/Canada - ?tats de l'Est
Objet: Transparency and trellis device

Dear R-users,

I am trying to produce trellis (png, or jpeg) graphs with transparent
background, but I cannot manage to make that happen. I tried to play around with
themes but to no avail. Any advise on the following example will be greatly
appreciated:

Thank you

Sebastien

####
library(lattice)

df <- data.frame(a=rep(1:4,4), b=rep(1:4,4), c=rep(1:4,each=4))

settings <- standard.theme()
settings <- modifyList(settings,
                       list(background=list(alpha=1,
                                            col="transparent")))
str(settings)

trellis.device(png,
               file="test.png",
               theme=settings)

myplot<-xyplot(b~a|c, data=df)

print(myplot)

dev.off()

####

Hi Deepayan,

Thank for you reply.
I am a little bit confused now. In the one hand, the trellis.device function has
lost his bg argument as explained in the Note section of ?trellis.device, but
the background info provided by a theme does not seem to impact the background
of the device. In the other hand, png has a bg argument that works great but no
"theme" capabilities as far as I could see.

Do you see a way to reconcile both sides of the problem?

Sebastien

----- Mail Original -----
De: "Deepayan Sarkar" <deepayan.sarkar at gmail.com>
?: pomchip at free.fr
Cc: r-help at stat.math.ethz.ch
Envoy?: Mercredi 5 Ao?t 2009 12h38:30 GMT -05:00 USA/Canada - ?tats de l'Est
Objet: Re: [R] Transparency and trellis device

On 8/5/09, pomchip at free.fr <pomchip at free.fr>
wrote:
> Just replying to bring back some attention on my post, which might have
slept
> through on Saturday.
>
>  Thank you for your help.
>
>
>  ----- Mail Original -----
>  De: pomchip at free.fr
>  ?: r-help at stat.math.ethz.ch
>  Envoy?: Samedi 1 Ao?t 2009 15h48:24 GMT -05:00 USA/Canada - ?tats de
l'Est
>  Objet: Transparency and trellis device
>
>
>  Dear R-users,
>
>  I am trying to produce trellis (png, or jpeg) graphs with transparent
background, but
>  I cannot manage to make that happen. I tried to play around with themes
but to no
>  avail. Any advise on the following example will be greatly appreciated:
This has nothing to do with trellis, your png device must be set up
with a transparent canvas when it is started. See the second paragraph
in the "Details" section of ?png, but basically

png("test.png", bg = "transparent")

-Deepayan

One thing that I did not mention is that my themes contain additional settings
(like margin definitions). By looking at the code of trellis.device, it look
like the operation of this function can be simplified a device opening followed
by a trellis.par.set call. Am I correct?
If so, I think I could replace my trellis.device call by the sequence
png("foo.png", bg="transparent") / trellis.par.set(mytheme).

Sebastien

----- Mail Original -----
De: "Deepayan Sarkar" <deepayan.sarkar at gmail.com>
?: pomchip at free.fr
Cc: r-help at stat.math.ethz.ch
Envoy?: Mercredi 5 Ao?t 2009 13h16:54 GMT -05:00 USA/Canada - ?tats de l'Est
Objet: Re: [R] Transparency and trellis device

On 8/5/09, pomchip at free.fr <pomchip at free.fr>
wrote:
> Hi Deepayan,
>
>  Thank for you reply.
>  I am a little bit confused now. In the one hand, the trellis.device
function has lost his bg argument as explained in the Note section of
?trellis.device, but the background info provided by a theme does not seem to
impact the background of the device. In the other hand, png has a bg argument
that works great but no "theme" capabilities as far as I could see.
>
>  Do you see a way to reconcile both sides of the problem?
There's no conflict. The "bg" argument of png() (and most other
devices) is a "canvas color" that is handled by the device driver. The
lattice "background" setting controls a background rectangle plotted
by lattice:

png("foo.png", bg = "transparent")
xyplot(1 ~ 1, par.settings = list(background = list(col = "yellow")))
dev.off()

Obviously, plotting a transparent rectangle over a white canvas (which
you were effectively doing) will not make the canvas transparent.

-Deepayan