R Under development (unstable) (2025-07-24 r88447 ucrt) -- "Unsuffered Consequences"
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> library("pixmap")
> 
> x <- read.pnm(system.file("pictures/logo.ppm", package="pixmap")[1])
> dx <- x@size
> chx <- getChannels(x)
> stopifnot(is(x, "pixmap"),
+           is(x, "pixmapRGB"),
+           dx == c(77, 101),
+           dim(chx) == c(dx, 3))
> par(mfrow = c(2,2))
> plot(x, main = "R logo pixmap")
> for(j in 1:3)
+     plot(pixmapGrey(chx[,, j]), main=paste("channel",j))
> 
> 
> x1 <- as(x, "pixmapGrey")
> z <- getChannels(x1)
> stopifnot(is(z, "matrix"),
+           dim(z) == dx)
> 
> x2 <- as(x1, "pixmapRGB")
> z <- getChannels(x2)
> stopifnot(is(z, "array"),
+           dim(z) == c(dx, 3))
> 
> proc.time()
   user  system elapsed 
   0.32    0.07    0.34