Photo Metadata

Fields

The module ships seven fields for the image media type, in config/optional so they are created only once an image media type exists (and, for keywords, a tags vocabulary):

Role	Field	Read from
coordinates	field_geo (geofield)	EXIF GPS, converted to signed decimal degrees
captured	field_captured (datetime)	EXIF DateTimeOriginal, then DateTimeDigitized, then IFD0 DateTime
camera	field_camera	EXIF Model
caption	field_caption	IPTC caption (2:120), then EXIF ImageDescription
credit	field_credit	IPTC by-line (2:80), then EXIF Artist
keywords	field_keywords (terms)	IPTC keywords (2:25)
focal_point	field_focal_point	The Focal Point crop, as x,y percentages from the top-left

To use fields a site already has, point a role at them in photo_metadata.settings:

drush config:set photo_metadata.settings fields.credit field_photographer

Set a role to '' and the module leaves it alone.

None of the fields is placed in a view display, and that is deliberate. A field added through the Field UI goes into the default view display, and the default view mode is often the one heroes and cards render media in. Metadata about a photograph should not appear under every picture on a site because a field was created, so a site that wants a credit line adds it to a display itself.

Uninstalling leaves the fields and their data. Captions and keywords are editorial content, and uninstalling a module is not a reason to delete them.

When files are read

On a media entity's first save, and whenever its file is replaced. An ordinary edit does not read the file again: with object storage in front of public:// that would mean downloading the photograph on every save. Values are written only into empty fields, so an editor's correction survives.

The focal point is copied on every save, and pushed to every media item showing a file whenever its crop changes, because the crop entity is what an editor edits.

Limits

• No XMP. PHP reads EXIF and IPTC, not XMP, and exiftool is not available on most hosts. Lightroom and Apple Photos write captions and keywords to XMP by default; copy them across to IPTC before importing.
• JPEG and TIFF only, for EXIF. PNG, WebP and HEIC carry nothing PHP can read.
• A zero GPS fix is discarded. Cameras that lose their fix write 0/0, which would otherwise put every such photograph in the Gulf of Guinea.
• Capture times have no zone. EXIF records the camera's clock, which is stored as written.

Commands

# How much of the library carries usable metadata.
drush photo-metadata:coverage

# Read metadata into every photograph missing it.
drush photo-metadata:backfill

# Re-read every file, discarding hand corrections.
drush photo-metadata:backfill --overwrite

Migrations

The photo_metadata process plugin reads the same values during an import, from a file ID, a stream wrapper URI or a local path:

process:
  field_geo:
    plugin: photo_metadata
    key: coordinates
    source: fid
  field_captured:
    plugin: photo_metadata
    key: captured
    source: fid

Keys are coordinates, captured, camera, caption, credit and keywords; keywords come back as a list of strings for entity_generate.