`as_bm_pixmap.rgba()` / `as_bm_pixmap.bitmap()` / `as_bm_pixmap.rawimg()`

[trevorld]

• "bitmap" "rgba" format returned by pdftools::pdf_render_page(..., numeric = FALSE). "rawimg" returned by webp::read_webp(). Supported for writing by png::writePNG(), jpeg::writeJPEG(), etc. Similar to {magick} format?
• Code of pdftools::pdf_render_page() suggests this could be as easy as:

as_bm_pixmap.rgba <- function(x, ...) {
  array <- aperm(structure(as.numeric(x) / 255, dim = dim(x)))
  as_bm_pixmap.array(array)
}