Creating a Color Wheel in R

Code for drawing a color wheel in R.

Note

Original Japanese version: Rで色相環を作成する

I originally wrote this code while trying several things with an algorithm called DeepFlow and looking for a figure to insert into the output. The implementation uses R.

When this kind of figure is drawn as a vector graphic such as PDF or SVG, the file becomes extremely heavy. It is better to draw it as a raster image such as PNG or JPEG. PNG is often a good choice because transparency is frequently useful.

len <- 1000
r <- seq(from = 0, to = 1, length.out = len)
theta <- seq(from = 0, to = 2 * pi, length.out = len)

plot(-1:1, -1:1, asp = 1, axes = FALSE, xlab = "", ylab = "", type = "n")
for (i in 1:len) {
  ri <- r[i]
  for (j in 1:len) {
    if (j == 1) {
      thetai0 <- 0
    } else {
      thetai0 <- theta[j - 1]
    }
    thetai1 <- theta[j]
    segments(
      ri * cos(thetai0),
      ri * sin(thetai0),
      ri * cos(thetai1),
      ri * sin(thetai1),
      col = hsv(h = thetai1 / (2 * pi), s = ri, v = 1)
    )
  }
}