When we call TextureProvider::cancelDecoding, we should make sure
that textures that have been decoded, but not yet used (popped)
should be released (i.e. memory freed and the meta data marked
appropriately.)
mipgen can now emit basis-encoded KTX2 files. Both the desktop and
web "suzanne" samples use this as a test for compressed textures.
This PR does not add KTX2 support to glTF, but it's on the way.
`BasisEncoder` has a builder style API that calls the basis encoder to
create KTX2 files. This hides some low-level BasisU features that we are
not using, like file I/O and mipmap generation.
`Ktx2Reader` is an easy-to-use API for creating Filament textures from
KTX2 files. Its API primarily consists of these two methods:
bool requestFormat(Texture::InternalFormat format);
Filament::Texture* load(const uint8_t* data, size_t size);
The first method is used to build an ordered list of formats that are
supported by your hardware. The second method consumes the contents of a
basis-encoded KTX2 file and attempts to produce a Filament texture with
a preferred format.
IMPORTANT: Our tools still let you use KTX1 for non-compressed images
because it is useful for HDR, but you can no longer use KTX1 for
block-compressed data.
Partial fix for #4771.
When creating a KTX file (e.g. with mipgen), you can of course choose
whether or not you want to use an sRGB format.
At load time, your app has an expectation about whether a particular
texture has an sRGB format. e.g. the glTF convention is that albedo
textures should be sRGB, while roughness textures are linear.
Before this commit, our KTX loader would look at the app's expectation,
then silently re-interpret the bits in the glTF texture in order to
match this expectation. This seems very wrong.
Instead, if the expectated format does not match the format in the KTX
file, we now print a warning.
Fixes#2422, which will also be obsoleted by our upcoming KTX2 support.
Changes:
- Remove the strange header-only variant of libs/image
- Rename KtxBundle => Ktx1Bundle
- Move image/KtxUtility => ktxreader/Ktx1Reader
- Add unit test for Ktx1Reader and test stub for KTX2.
Notes:
- Ktx1Bundle does not depend on Filament and is used by cmgen
and mipgen to generate KTX files.
- Ktx1Reader has a dependency on Filament and should therefore live in
a separate library, which it now does.
