manipulate annotations from ngscene

[jefferis]

• Ideally would allow annotations to set and retrieved using the same interface as the csv in the neuroglancer interface i.e. with a data.frame intermediate
• some columns may need to be compound

[jefferis]

There was some WIP code. Currently looks like:

decode_annotes <- function(x) {
  if(inherits(x, 'nglayers')) {
    ann=x[[1]]
  } else {
    sc=ngl_decode_scene(x)
    type <- NULL # for R CMD check
    ann=ngl_layers(sc, type=='annotation')[[1]]
  }

  if(!isTRUE(ann$tool=='annotatePoint'))
    stop("Only point annotations can be converted to a dataframe",
         " but you can still process them manually!\n",
         "See ?")
  process_segs <- function(x) {
    if(is.null(x)) x="0"
    if(length(x)>1) x=paste(x, collapse = ", ")
    x
  }
  l = lapply(ann$annotations, function(p)
    tibble::tibble(
      x = p$point[1],
      y = p$point[2],
      z = p$point[3],
      type = p$type,
      segments = process_segs(p$segments),
      id = p$id
    ))
  df=dplyr::bind_rows(l)
  df
}