If we have a valid PNG header with geometry info etc, we should still
display it as *something*, even if the image data itself is missing or
corrupted.
This matches the behavior of other browsers, and is something that
Cloudflare Turnstile checks for.
To achieve this, we split the PNG decoder's initialization into two
steps: "everything except reading frame data" and "reading frame data".
If the latter step fails, we yield a transparent bitmap with the
geometry from the PNG's IHDR chunk.
Before, libpng would use its own internal logging mechanism to print
non-fatal errors and warnings to stdout/stderr. This made it confusing
when trying to search the Ladybird codebase for those messages as they
didn't exist.
This commit uses `png_set_error_fn` from libpng to redirect those
messages to our own custom logging functions instead.
This patch introduces the `Gfx::ColorSpace` class, this is basically a
serializable wrapper for skia's SkColorSpace. Creation of the instances
of this class (and thus ICC profiles parsing) is performed in the
ImageDecoder process. Then the object is serialized and sent through
IPC, to finally be handed to skia for rendering.
However, to make sure that we're not making all LibGfx's users dependent
on Skia as well, we need to ensure the `Gfx::ColorSpace` object has no
dependency on objects from Skia. To that end, the only member of the
`ColorSpace` class is the opaque `ColorSpaceImpl` struct. Though, there
is on issue with that design, the code in `DisplayListPlayer.cpp` needs
access to the underlying `sk_sp<SkColorSpace>`. It is provided by a
template function, that is only specialized for this type.
Doing this work allows us to pass the following WPT tests:
- https://wpt.live/css/css-color/tagged-images-001.html
- https://wpt.live/css/css-color/tagged-images-003.html
- https://wpt.live/css/css-color/tagged-images-004.html
- https://wpt.live/css/css-color/untagged-images-001.html
Other test cases can also be found here:
- https://github.com/svgeesus/PNG-ICC-tests
Note that SkColorSpace support quite a limited amount of color spaces,
so color profiles like the ones in [1] or the v4 profiles in [2] are not
supported yet. In fact, SkColorSpace only accepts skcms_ICCProfile with
a linear conversion to XYZ D50.
[1] https://www.color.org/browsertest.xalter
[2] https://www.color.org/version4html.xalter
