%YAML 1.1
---
$schema: "http://stsci.edu/schemas/yaml-schema/draft-01"
id: "http://stsci.edu/schemas/asdf/transform/healpix-1.1.0"
title: |
  HEALPix projection.

description: |
  Corresponds to the `HPX` projection in the FITS WCS standard.

  Invertibility: All ASDF tools are required to provide the inverse of
  this transform.

allOf:
  - $ref: "transform-1.1.0"
  - type: object
    properties:
      direction:
        enum: [pix2sky, sky2pix]
        default: pix2sky

      H:
        type: number
        description: |
          The number of facets in the longitude direction.
        default: 4.0

      X:
        type: number
        description: |
          The number of facets in the latitude direction.
        default: 3.0
...
