Animate a sketch plot by "boiling" its lines

Renders a ggplot built with ggsketch geoms nframes times, shifting every roughening seed by a per-frame amount, so the whole drawing shimmers and re-draws itself like a hand-animated cel (the "boiling line" effect). Because the shift is added to every resolved seed – whether a layer set its own seed or inherited the global one – a plot boils without any change to its code. Frame 1 reproduces the static plot exactly.

Usage

animate_sketch(
  plot,
  nframes = 12L,
  fps = 10,
  type = c("boil", "draw_on"),
  direction = c("lr", "rl", "bt", "tb", "diag", "radial"),
  easing = c("linear", "ease_in", "ease_out", "ease_in_out"),
  file = NULL,
  width = 7,
  height = 5,
  units = "in",
  res = 120,
  background = "white",
  device = NULL,
  seed = NULL,
  renderer = c("auto", "gifski", "magick", "none"),
  loop = TRUE
)

Arguments

plot

A ggplot object using ggsketch geoms.

nframes

Number of frames. Default 12.

fps

Frames per second in the output GIF. Default 10.

type

Motion type: "boil" (re-seed the wobble each frame so the whole drawing shimmers) or "draw_on" (progressively reveal the finished drawing behind a moving wipe, as if a hand were drawing it).

direction

For type = "draw_on", how the drawing is revealed: a straight wipe "lr" (left-to-right, default), "rl", "bt" (bottom-to-top) or "tb"; a diagonal wipe "diag" (top-left to bottom-right); or "radial" (a circular iris opening from the centre).

easing

For type = "draw_on", the pacing of the reveal across frames: "linear" (constant speed, default), "ease_in" (start slow), "ease_out" (end slow), or "ease_in_out" (slow at both ends).

file

Output GIF path. If NULL (default), no GIF is written and the frame paths are returned invisibly.

width, height, units, res

Frame size and resolution, passed to the graphics device (units one of "in", "cm", "mm", "px").

background

Frame background colour. Default "white".

device

Graphics device: "ragg" (default when installed) or "png".

seed

Base seed (NULL uses getOption("ggsketch.seed", 1L)).

renderer

GIF backend: "auto" (default), "gifski", "magick", or "none" (always return frame paths).

loop

Loop the GIF forever? Default TRUE.

Value

Invisibly, the GIF path (when written) or a character vector of frame image paths.

Details

Frames are stitched into a GIF when gifski or magick is installed (neither is a hard dependency); otherwise the frame image paths are returned so you can assemble them yourself. Everything is reproducible: the same seed yields the same animation.

Examples

# \donttest{
library(ggplot2)
p <- ggplot(mpg, aes(class)) +
  geom_sketch_bar(fill = "#7BAFD4", seed = 1L) +
  theme_sketch()
# Write a GIF if gifski/magick is available, else get frame paths back:
gif <- animate_sketch(p, nframes = 8, file = tempfile(fileext = ".gif"))
# }