When using the heif10Representation
and writeHEIF10Representation
APIs of CIContext
, the resulting image doesn’t contain an alpha channel.
When using the heifRepresentation
and writeHEIFRepresentation
APIs, the alpha channel is properly preserved, i.e., the resulting HEIC will contain a urn:mpeg:hevc:2015:auxid:1
auxiliary image. This image is missing when exporting as HEIF10.
Is this a bug or is this intentional? If I understand the spec correctly, HEIF10 should be able to support alpha via auxiliary image (like HEIF8).