Tag representations are not decoder- or encoder-specific, so should live
in their own module accessible to both for reuse. The decoder::ifd
module remains since this module is mainly dedicated to decoding the
IFD.
Resolve several TODOs where tag values were cast from u32 without checks
by providing generic methods that error when the value fails casting to
the desired type. In addition to being more correct, this simplifies and
shortens decoding logic.
Remove `find_tag_u32` and `find_tag_u32_vec` as they are now redundant
and a GitHub code search found no usages outside copies of
`image-tiff`.
Make the behavior of RGB and RGBA like Gray in returning ColorTypes for
all homogeneous bit depths, even if those depths are not 8, 16, 32 or
64. Note that this does not change which color types can actually be
decoded.
Note that this adds the LONG8 data type from BigTIFF because of bounds
requiring TiffValue. However, this datatype should not actually be
written to tags.
This makes it cheaper to introduce new features that might require
amending the list of variants by allowing us to introduce previously
uncovered causes or more specialized representations.
It encapsulates the implementation detail of holding a miniz_oxide
status within. The derived traits are not too extensive for other
possible representations as well.
Avoids leaking the dependency on `miniz_oxide` into the public interface
by making a constructor taking a status argument crate internal. It
would otherwise not be possible to replace the deflate decoder without
breaking that interface.
The discriminant of some enum types can be retrieved with the `as`
operator and in C style enums it is also possible to set a specific
discriminant. However, that may silently change—breaking the value
written to the file. It is better to use that technique mostly for ffi
purposes.
Several other uses that currently rely on num-traits for conversion have
no Unknown representation. Thus, the converter now outputs only known
variants or an error and the exposing function then can put the error
value into an Unknown variant instead.
Factor out parts that are unique to instantiations such as the name, the
documentation, the underlying type, the public conversion methods.
Also adds the ability to document individual items and remodels the
syntax to more closely resemble ordinary enum definitions.
Andrew Champion