Skip to content

rfc4: clarify coordinate direction convention #428

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
thewtex wants to merge 1 commit into
base: main
Choose a base branch
from
Open

rfc4: clarify coordinate direction convention #428

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
11 changes: 11 additions & 0 deletions rfc/4/index.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -77,6 +77,16 @@ This metadata MUST only be used in cases where there is a single subject in the

The `orientation` field is structured as an object and MUST have a `type` field that specifies the orientation domain (e.g., "anatomical") and MUST have a `value` field that specifies the specific orientation within that domain. Valid `type` strings are defined in this document -- currently only `"anatomical"`.

### Coordinate Direction Convention

The directional orientation values (e.g., "anterior-to-posterior", "left-to-right") specify the direction from negative to positive coordinates along the axis. For example, an axis with `"orientation": {"type": "anatomical", "value": "anterior-to-posterior"}` indicates that:

- Coordinate values increase from the anterior (front) toward the posterior (back)
- The most anterior position has the smallest coordinate value
- The most posterior position has the largest coordinate value

This convention aligns with the axis coordinate system defined by the spatial metadata specified elsewhere in the NGFF specification. The `orientation` field provides semantic meaning to the coordinate direction already established by these spatial transforms.

### Example

For anatomical data, an example axis configuration would look like:
Expand Down Expand Up @@ -484,3 +494,4 @@ End-user applications SHOULD display the encoded information with, for example,
| 2025-07-17 | Updated field name from `anatomicalOrientation` to `orientation` with structured `type`/`value` approach to support extensibility to other orientation domains. | [https://github.com/ome/ngff/pull/318](https://github.com/ome/ngff/pull/318) |
| 2025-07-23 | Clarify that the type fields are MUST's and the only currently defined value is "anatomical". | [https://github.com/ome/ngff/pull/329](https://github.com/ome/ngff/pull/329) |
| 2025-07-23 | Use a Pydantic Literal for anatomical type | [https://github.com/ome/ngff/pull/330](https://github.com/ome/ngff/pull/330) |
| 2026-01-20 | Clarify coordinate direction convention | [https://github.com/ome/ngff/pull/428](https://github.com/ome/ngff/pull/428) |