Add DDS image load and save functionality

[fire]

See: godotengine/godot-proposals#5748

The proposal involves adding the ImageLoaderDDS class, moving the DDS handling code inside it, and reusing the image loader (or part of it) in the texture loader in the future.

We are not supporting saving non-2d textures at this moment. Feature enhancement wanted.

• BetsyCompressor has a runtime execution error Rendering team is handling it.
• Only handle saving 2d-textures (like not 3d or 2d arrays)
• Pass GitHub actions tests
• Expand the list of supported Image::Formats and DDSFormats
• Extract common header from DDS reader and DDS writer
• Debug why BPTC dds loading isn't working
  • Fix BPTC unit test
• Stress test the system with an example project https://v-sekai.github.io/manuals/decisions/20250122-VRChat-Loader-with-Godot-Engine.html
  • In a GDScript project, create a web server (Godot Engine) to export from its current scene with all images repacked as a GLTF2 binary DDS and png/jpeg on HTTP GET.
  • https://github.com/V-Sekai-fire/godot-http-glb-host
• Add Image.load_dds_from_buffer()
• Add Image.save_dds_from_buffer()
• Error save_dds(const String &p_path) const
• Vector<uint8_t> save_dds_to_buffer() const
• Refactor DDS image preparation, update function signatures, and improve mipmap handling
• Enhance DDS functionality by adding image saving, buffer handling, and loading capabilities
• Expand DDS tests with image format conversions, metric checks, and compression methods
• Update the DDS loader to use buffers in tests and handle unsupported formats
• Improve DDS image saver to handle all mipmap levels and validate data sizes
• Fix include guards and formatting in DDS image saver header files

[bruvzg]

If info from the related MoltenVK issue I have mentioned here is correct, changing CI from runs-on: macos-latest to runs-on: macos-15 might fix the macOS issue (even if we won't use it since it's a preview image, it's probably worth checking just to confirm).

[fire]

@bruvzg Is it possible/advisable to check for macOS-15 or newer at runtime?

[bruvzg]

Is it possible/advisable to check for macOS-15 or newer at runtime?

Yes:

if (@available(macOS 15.0, *)) {
// If it's Objective-C code.
}

or

if (__builtin_available(macOS 15.0, *)) {
// If it's C++ code.
}

[fire]

How do I invert it? I want an if not macOS 15.0 or greater, then return.

if (__builtin_available(macOS 15.0, *)) {
// If it's C++ code.
}

[fire]

Commentary in rocketchat mentioned:

1. betsy isn't falling back properly in a headless environment
2. Suggest that we write dds directly with uncompressed images

[BlueCube3310]

Tested this with all supported Image formats (uncompressed + s3tc + rgtc + bptc), some images fail to save. This diff should fix that and BGRA4 channel swapping: dds_uncomp.patch

Regarding RGB565: It saves correctly, but it looks like the renderers (both RD and Compatibility) expect the colors to be stored as BGR565, while the Image class operates on RGB565.

Edit: Here's a testing project:
dds-saveload-test.zip

[BlueCube3310]

#103635 should fix the issues with RGB565, otherwise this PR looks good in terms of functionality

[BlueCube3310]

Tested this with several different DDS files, loading still works correctly, saving also works. This will make it easier to debug compressed/VRAM-specific images