Re: [Rd] raster support in graphics devices

From: baptiste auguie <>
Date: Mon, 14 Dec 2009 16:09:15 +0100


[my message below is a bit off-topic]

2009/12/14 Paul Murrell <>:

> I have thought a bit about drawing the same image multiple times (more in
> the context of using a bitmap for a plotting symbol).  I imagine something
> like being able to "add" a raster image to a device and then simply "refer"
> to that image (e.g., by name) is needed.

That would be nice.

I first thought that this new rasterGrob would be a good way to implement some kind of filling pattern for grid graphics, but after some more testing I was surprised to see that a similar approach with vector patterns could result in more efficient, better output. Of course raster filling patterns could still be nice to have for fancy images or gradients.

One thing that worries me with the approach I've taken below is that the grob is not vectorized. In particular, if one was to use it as a building block for histograms (as in base graphics' density parameter) each rectangle would have to be drawn in sequence. I can of course Vectorize() this grob into a new one (gTree) but I haven't seen any examples like this before. Does this sound reasonable? (argument explosion might be another problem...)

Best regards,


Below is the gist of my experiments (the first part is not related to grid.raster and runs in current R).


## vector patterns
grid.vpattern(x=0.2, width=unit(3,"cm"), height=unit(0.5,"npc"),

             motif="points", motif.params=list(pch=22,
                               gp=gpar(cex=0.8, lwd=5, col="grey90",
fill="grey95")), clip=T)

grid.vpattern(x=0.5, width=unit(0.3,"npc"), height=unit(0.5,"npc"),

             motif="segments", motif.params=list(angle=45,
                                 gp=gpar(lty=2, col="grey", lwd=2.4)))

grid.vpattern(x=0.5, y=0.9, width=unit(0.5,"npc"), height=unit(1,"cm"),
             motif="points", motif.params=list(pch="+"), clip=F,
pattern.offset=c(1, 0.5))

grid.vpattern(x=0.8, width=unit(0.2,"npc"), height=unit(0.2,"npc"),

             motif="grid", motif.params=list(angle=45,
                             gp=gpar(lwd=10, col="grey90")), clip=T,
pattern.offset=c(-1, 0.5))

grid.vpattern(x=0.5, y=0.1, width=unit(0.9,"npc"), height=unit(0.1,"npc"),

             motif="grid", motif.params=list(angle=30, gp=gpar(col="red")),
              gp=gpar(alpha=0.1, fill="red"))

## raster patterns


## a raster motif
plus <- function(..., width=5, height=5){   x11(width=width/25.4, height=height/25.4)   grid.points(x=unit(0.5, "npc"), y=unit(0.5, "npc"),

              pch=3, size=unit(2, "mm"), gp=gpar(), ...)   m <- grid.cap()
.plus <- plus()

g1 <- rpatternGrob(x=0.5, y=0.4, width=unit(3.7, "cm"),

                   height=unit(0.4, "npc"),
grid.draw(g1) mailing list Received on Mon 14 Dec 2009 - 15:11:14 GMT

This archive was generated by hypermail 2.2.0 : Mon 14 Dec 2009 - 21:21:05 GMT