distorted_R_animation.R

library(ggplot2)
library(patchwork)
library(dplyr, warn.conflicts = FALSE)

d <- string2path::string2path("R", "Arial")

max_dist <- 0.003

d2 <- d |> 
  group_by(glyph_id, path_id) |> 
  summarise(
    slider::slide2_dfr(x, y, \(x, y) {
      if (length(x) == 1L) {
        return(vctrs::data_frame(x = x, y = y))
      }
      
      dist <- sqrt((x[2] - x[1])^2 + (y[2] - y[1])^2)
      
      if (dist < max_dist) {
        # 1つ目は前の区間に含まれているので取り除く
        return(vctrs::data_frame(x = x[2], y = y[2]))
      }
      # max_distを超えない最大の長さになるように分割する
      n <- ceiling(dist / max_dist)
      
      if (identical(x[1], x[2])) {
        # approxはX軸に垂直だと使えない
        vctrs::data_frame(x = x[1], y = seq(y[1], y[2], length.out = n))
      } else {
        out <- approx(x, y, n = n)
        # 1つ目は前の区間に含まれているので取り除く
        vctrs::data_frame(x = out$x[-1], y = out$y[-1])
      }
    }, .before = 1L),
    .groups = "drop"
  )

steps <- 150
pt <- c(0.5, 0.5)
gifski::save_gif(
  for (i in seq_len(steps)) {
    x <- 0.3 + 0.23 * i / steps * cos(28 * i / steps)
    y <- 0.3 + 0.23 * i / steps * sin(23 * i / steps)
    pt <- c(x, y)
    m <- cbind(d2$x, d2$y)
    m2 <- t(apply(m, 1, function(row) {
      dist <- sqrt(sum((row - pt)^2))
      row + (row - pt) / dist * (i / steps)^1.4
    }))
    
    d_tmp <- d2 |> 
      mutate(x = m2[, 1], y = m2[, 2])
    
    p <- ggplot(d_tmp, aes(x, y)) +
      geom_path(aes(group = path_id, colour = factor(path_id))) +
      geom_point(aes(colour = factor(path_id)), size = 2) +
      geom_point(data = data.frame(x, y), size = 10, colour = "black") +
      coord_fixed() +
      theme_void() +
      guides(colour = "none")
    print(p)
  },
  delay = 1 / 60
)