# `Storehouse.Analyzer.EditMetadata`
[🔗](https://github.com/hattoriai/storehouse/blob/v0.2.0/lib/storehouse/analyzer/edit_metadata.ex#L1)

A step (`Storehouse.Analyzer`) that edits the metadata inside a stored
file without re-encoding it, and writes the edited file back over the
original, under `"edit_metadata"`.

It does nothing unless asked: an app adds it to its steps, with what to
change.

    # Where photos were taken, removed before they are shown.
    Storehouse.analyze(file, [{Storehouse.Analyzer.EditMetadata, strip: :gps}])

    # Only a few tags kept, and the author's name written in.
    Storehouse.analyze(file, [
      {Storehouse.Analyzer.EditMetadata,
       strip: {:keep, [:orientation, :copyright]},
       put: %{artist: "Ana Sousa", copyright: "© Ana Sousa"}}
    ])

Options:

  * `:strip` - `:gps`, or `{:keep, tags}` (`Storehouse.Image.MetadataEditor`).
  * `:put` - tags to write, or remove with `nil`, after `:strip`.
  * `:editor` - what makes the changes (`Storehouse.Image.MetadataEditor`).
    The default is `config :storehouse, :metadata_editor`, else
    Storehouse's own, `Storehouse.Image.MetadataEditor.Builtin`, which edits
    JPEG, PNG and WebP.

With neither change, or for a type the editor does not edit, the step
is `:skipped` and the file left as it is. A file the editor cannot read
fails the step, with why, and the stored file is left as it was.

Its result: `"changed"`, whether the file was rewritten; and when it
was, its `"bytes"` and `"checksum"` now, and what was done
(`"stripped"`, `"put"`). The steps after it read the edited file.

## Checksums

The file's `:checksum` stays the one of the file as it was uploaded,
which is what `:existing` compares to find the same upload again
(`Storehouse.store/2`): an upload of the same photo still finds it. The
checksum of what is stored now is the step's `"checksum"`, and
`Storehouse.checksum/1` gives it of a copy.

---

*Consult [api-reference.md](api-reference.md) for complete listing*