Demand for AVIF support on the web is growing, as the word gets out
about this new file format which allows higher-quality encoding at
smaller sizes. Core contributors to major open-source CMSs are
interested in auto-generating AVIF images! They've been simply
waiting for support to appear in libgd.
This PR aims to meet the growing demand, and to help bring smaller,
more beautiful images to more of the web - to sites created by
experienced developers and CMS users alike.
This PR adds support by incorporating libavif in addition to the
existing libheif support. It's generally felt that libavif has
more complete support for the AVIF format. libavif is also used
by the Chromium project and squoosh.app.
In this PR, I've endeavored to incorporate the latest research into
best practices for AVIF encoding - not just for default quantizer
values, but also an algorithm for determining the number of
horizontal tiles, vertical tiles, and threads.
Fixes#557.
With the adoption of AVIF by Firefox and Chromium based browsers (still
in experimental phase), the newer incorporation of HEIF by Canon and Sony
in their cameras and the newer support of both of them in modern software
like ImageMagick, GIMP and Krita, `gd` haven't seen any endorsement for
the formats up until this PR.
Reading and writing is done by `libheif`, with functionality for chroma
subsampling (for now `4:2:0`, `4:2:2` and `4:4:4`), quality (with new
`200` for lossless) and compression (whether `HEVC` or `AV1`) selection.
This was tested with `libheif` version `1.11.0` in my Solus machine.
Also, fixes both #395 and #557.
Specified calling convention on function pointers. (This matters
under Windows).
Switched from rindex() to strrchr() (oops!).
Tidied the formatting a bit.
These are convenience functions which load or save image data to a
file. They are roughly equivalent to opening a file handle with
fopen() and calling gdImageCreateFrom*() or gdImage*() on the FILE
pointer. However, these functions identify the input or output format
from the filename suffix and call the appropriate read or write
function accordingly.
gdSupportsFileType() can be used to test if a specific file format
is supported.
Most scripting interfaces already do something like this but now
there's support for doing it from C as well.
This change also adds test cases for the code and naturaldocs
documentation.
Ben Morss
Martin Reboredo
Mike Frysinger
Wangkun
Chris Reuter