Looping mutates

[KaiAragaki]

It appears that when using for loops, magick acts much like the values are passed by reference rather than value (understandable, as these are externalptrs). However, I found this behavior a bit unexpected.

Toy example:

library(magick)

cutter <- function(imgs) {
  for (i in seq_along(imgs)) {
    img <- magick::image_crop(imgs[i], "100")
    imgs[i] <- img
  }
  imgs
}

image_info(logo)
#>   format width height colorspace matte filesize density
#> 1    GIF   640    480       sRGB FALSE    28576   72x72
image_info(cutter(logo))
#>   format width height colorspace matte filesize density
#> 1    GIF   100    480       sRGB FALSE        0   72x72
image_info(logo)
#>   format width height colorspace matte filesize density
#> 1    GIF   100    480       sRGB FALSE        0   72x72

[dcaud]

One part that is odd is that the final image_info doesn't do what I expect. But when reading the logo in from disk each call, it does do what I expect:

image_info(image_read("logo:"))
image_info(cutter(image_read("logo:")))
image_info(image_read("logo:"))

Your cutter function never modifies logo, so I continue to be stumped as to what is happening.