thank_you_solid_stars.R

library(showtext)
library(fontr)
library(tidyverse)
library(transformr)
library(animation)
library(ggpolypath)

# use showfont to load the font
font_add_google("Allura")

# use fontr to extract letter forms
get_letter <- function(ch, xshift, yshift, id) {
  char_poly <-  glyph_polygon(
    ch, family = "Allura", 
    face = "regular", nseg = 20)
  char_poly$x <- (char_poly$x * 1.9) + xshift
  char_poly$y <- (char_poly$y * 1.9) + yshift
  char_poly$id <- id
  return(char_poly)
}

# use transformr to add stars
get_shape <- function(xshift, yshift, id) {
  shape_poly <- poly_star()
  shape_poly$y <- ((shape_poly$y + 1) / 2.5) + yshift
  shape_poly$x <- (shape_poly$x / 2.5) + xshift
  shape_poly$id <- id
  return(shape_poly)
}

# spacer
na_row <- tibble(x = NA, y = NA, id = NA)

# specify stars 
sep <- .75
shapes <- bind_rows(
  get_shape(1.5,sep,1), na_row,
  get_shape(2.4,sep,2), na_row,
  get_shape(3.3,sep,3), na_row,
  get_shape(4.2,sep,4), na_row,
  get_shape(5.1,sep,5), na_row,
  get_shape(2.4,-sep,6), na_row,
  get_shape(3.3,-sep,7), na_row,
  get_shape(4.2,-sep,8)
)

# specify text
msg <- bind_rows(
  get_letter("T", 1.2, sep, 1), na_row,
  get_letter("h", 2.2, sep, 2), na_row,
  get_letter("a", 3.1, sep, 3), na_row,
  get_letter("n", 4.0, sep, 4), na_row,
  get_letter("k", 4.8, sep, 5), na_row,
  get_letter("Y", 2.2, -sep, 6), na_row,
  get_letter("o", 3.2, -sep, 7), na_row,
  get_letter("u", 3.9, -sep, 8)
)

nf <- 50

tweened <- tween_polygon(shapes, msg, 
  ease = "cubic-in-out", nframes = nf) 

tweened <- bind_rows(
  tweened, tweened %>% mutate(.frame = (2*nf+1)-.frame)) %>% 
  arrange(.frame) %>%
  as_tibble()

drawframe <- function(data, f, alpha = .5) {
  df <- data %>% 
    filter(.frame == f)
  df$branch <- is.na(df$x)
  df$branch <- cumsum(df$branch) + 1
  pic <- df %>%
    filter(!is.na(x)) %>%
    ggplot(aes(x, y, group=branch)) +  
    geom_polypath(show.legend = FALSE, 
                  fill="black", alpha = alpha) + 
    coord_equal() +
    ylim(-2, 3) + 
    theme_void()
  plot(pic)
}

# save the gif using animation::saveGIF
saveGIF(
  expr = {for(f in 1:(nf*2)) drawframe(tweened, f)}, 
  movie.name = "~/../Desktop/thank_you_solid_stars.gif",
  nmax = nf*2,
  interval = 3/nf
)