library(gridSVG)
library(lattice)
library(grid)
pdf(NULL)
bwplot(voice.part ~ height, data=lattice::singer, 
       xlab="Height (inches)",
       par.settings=list(box.rectangle=list(col="black"), 
                         box.umbrella=list(col="black"), 
                         plot.symbol=list(col="black")))
# grid.ls()
# Looks like boxes are all called <something>bwplot.box.polygon<something>
# Create linear gradient
fill <- linearGradient(c("black", "white"),
                       y0=.5, y1=.5,
                       gradientUnits="coords")
# Register gradient now so it applies to the whole page
registerGradientFill("br", fill)
# Fill each box with gradient
grid.gradientFill("bwplot.box.polygon", label=rep("br", 17), grep=TRUE,
                  group=FALSE)
# Generate SVG version (where the gradient will actually show up)
grid.export("Figures/export-lattice-gradientfill.svg")
dev.off()
system("inkscape --export-pdf=Figures/export-lattice-gradientfill.pdf Figures/export-lattice-gradientfill.svg")
system("convert Figures/export-lattice-gradientfill.pdf Web/export-lattice-gradientfill.png")