I am trying to reproduce some code from this repo:

library(magick)
#> Linking to ImageMagick 6.9.11.60
#> Enabled features: fontconfig, freetype, fftw, heic, lcms, pango, webp, x11
#> Disabled features: cairo, ghostscript, raw, rsvg
#> Using 64 threads

library(sf)
#> Linking to GEOS 3.10.2, GDAL 3.4.1, PROJ 8.2.1; sf_use_s2() is TRUE

library(tidyverse)
i <- 
image_read('https://images.photowall.com/products/59143/audrey-hepburn-3.jpg?h=699&q=85') |> 
image_resize("300x")



# Define some variables for this step
size <- 300
n_shades <- 16

i_processed <-
  i |>
  image_resize(paste0(size,"x",size,"^")) |>
  image_crop(geometry = paste0(size,"x",size), gravity = "center") |>
  image_convert(type = "grayscale") |>
  image_quantize(max = n_shades, dither=FALSE) |>
  image_flip()

i_processed

i_sf <- 
  i_processed |> 
  image_raster() |> 
  mutate(
    col2rgb(col) |> t() |> as_tibble(),
    col = scales::rescale(red, to = c(1,0))) |> 
  select(-green, -blue, -red) |> 
  stars::st_as_stars() |> 
  st_as_sf(as_points = FALSE, merge = TRUE) |> 
  st_make_valid() |> 
  st_set_agr("constant") |> 
  st_normalize()

However, in this step the function rescale does not create the object red.

This the obtained error:

Error in eval(cols[[col]], .data, parent.frame()) : 
  object 'red' not found

^{Created on 2024-06-21 with reprex v2.1.0}