SVG to PNG

Posted on June 17, 2022 by Stéphane Laurent

Tags: R, graphics

Here is a way to get a high-quality PNG image with R: save it as SVG first, then convert the SVG file to a PNG file, with the rsvg package.

Let’s see. I construct a hyperbolic Delaunay triangulation with the gyro package:

library(gyro)

phi <- (1 + sqrt(5)) / 2
theta <- head(seq(0, pi/2, length.out = 11), -1L)
a <- phi^((2*theta/pi)^0.8 - 1)
u <- a * cos(theta)
v <- a * sin(theta)
x <- c(0, u, -v, -u, v)
y <- c(0, v, u, -v, -u)
pts <- cbind(x, y) / 1.07

hdel <- hdelaunay(pts, model = "U")

fcolor <- function(t){
  RGB <- colorRamp(hcl.colors(20L, "Berlin"))(t)
  rgb(RGB[, 1L], RGB[, 2L], RGB[, 3L], maxColorValue = 255)
}

Now let’s save the plot as a PNG, directly:

png("hdelaunayU.png", width = 512, height = 512)
plotHdelaunay(
  hdel, vertices = FALSE, color = fcolor
)
dev.off()

And now let’s save it as SVG then convert it to PNG:

svg("hdelaunayU.svg")
plotHdelaunay(
  hdel, vertices = FALSE, color = fcolor
)
dev.off()

rsvg::rsvg_png(
  "hdelaunayU.svg", "hdelaunayU_from_svg.png",
  width = 512, height = 512
)

Observe the difference: