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Resolve a document's asset paths under a local root

Source: R/root-funs.R
update_root.Rd

Returns a copy of an in-memory STAC document whose assets point at their on-disk locations under a local root_dir, following the canonical static catalog layout used by stac_save(). For every asset with a relative href, the local_path attribute is set to the file's location under root_dir; assets whose href is already an absolute path or a URL are returned unchanged.

update_root() is generic and dispatches on the document class:

  • doc_item: assets resolve under root_dir/stac/collections/<collection>/items/<id>/. The collection is read from the item's own collection field, so build the item with new_item(collection = ...) (or save it first, which stamps the field).

  • doc_collection: assets resolve under root_dir/stac/collections/<id>/, which covers a collection-level thumbnail propagated from its items.

It is a pure helper: it reads no raster and writes no file. Its purpose is to make files produced by stac_save() – such as a thumbnail PNG rendered into the item directory – resolvable by plot() and other local readers, which consult an asset's local_path attribute before falling back to its href.

Usage

update_root(x, root_dir)

# S3 method for class 'doc_item'
update_root(x, root_dir)

# S3 method for class 'doc_collection'
update_root(x, root_dir)

Arguments

x

A doc_item from new_item() or a doc_collection from new_collection().

root_dir

A character directory under which the stac/ tree was written by stac_save().

Value

The document x, with the local_path attribute set on each asset that has a relative href.

Examples

root <- tempfile("stac-")
col <- new_collection("land-cover", "Land Cover", "Example collection")
item <- new_item(
  "land-cover-2022",
  bbox = c(-50, -10, -49, -9),
  collection = col,
  assets = list(data = new_asset("data.tif", title = "Data"))
)
stac_save(collection = col, items = item, root_dir = root)

item <- update_root(item, root)
attr(item$assets$data, "local_path")
#> [1] "/tmp/Rtmplox5oF/stac-1d2ba69ac53/stac/collections/land-cover/items/land-cover-2022/data.tif"