The byte count for strips is the compressed length. The compressed
length may be larger than the uncompressed length, especially with poor
compression choices (multi-byte samples with packbits) or small images.
Convert most unchecked size/index `as` casts to checked casts with
`TryFrom`, included another top-level error variant.
This has several motivations:
- Making the library as robust as possible, including to platform
differences.
- Unchecked casts are susceptible to breakage during refactorings.
- Preparing for BigTIFF support, which will require the introduction of
generics and associated types for some parts of the de/encoders.
Unchecked primitive casts cannot be bound, while TryFrom can, and
overflowing conversions become more likely.
- Remaining u16 casts may be prone in failure in existing practice and
not just in theory during future changes.
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.
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