feat(tex): add has_opaque_alpha for crunch

include/btu/tex/crunch_texture.hpp

@@ -42,6 +42,8 @@ class CrunchTexture
     [[nodiscard]] auto get_texture_type() const noexcept -> TextureType;
     [[nodiscard]] auto get_format_as_dxgi() const noexcept -> DXGI_FORMAT;
 
+    [[nodiscard]] auto has_opaque_alpha() const noexcept -> bool;
+
     [[nodiscard]] auto operator==(const CrunchTexture &) const noexcept -> bool = default;
 
 private:

src/tex/crunch_texture.cpp

@@ -111,6 +111,40 @@ auto CrunchTexture::get_format_as_dxgi() const noexcept -> DXGI_FORMAT
     }
 }
 
+auto CrunchTexture::has_opaque_alpha() const noexcept -> bool
+{
+    if (!tex_.has_alpha())
+        return true;
+
+    // Check if there are any miplevels at all.
+    [[unlikely]] if (!tex_.get_num_levels())
+        return true;
+
+    // Should catch everything.
+    const uint8 threshold = 254;
+
+    for (auto face = 0u; face < tex_.get_num_faces(); face++)
+    {
+        const auto *mip = tex_.get_level(face, 0);
+
+        const auto img = mip->get_image();
+
+        // One last safety check.
+        [[unlikely]] if (img == nullptr)
+            return true;
+
+        const auto pixels = img->get_pixels();
+
+        for (auto i = 0u; i < img->get_total_pixels(); i++)
+        {
+            if (pixels[i].a < threshold)
+                return false;
+        }
+    }
+
+    return true;
+}
+
 auto load_crunch(Path path) noexcept -> tl::expected<CrunchTexture, Error>
 {
     CrunchTexture tex;

tests/tex/crunch.cpp

@@ -73,6 +73,21 @@ TEST_CASE("Crunch Tex Memory IO", "[src]")
     REQUIRE(*mem_data == fs_data);
 }
 
+TEST_CASE("Crunch Tex has_opaque_alpha", "[src]")
+{
+    const auto dir             = Path("crunch");
+    const auto opaque_file     = dir / "in" / u8"opaque_alpha.dds";
+    const auto not_opaque_file = dir / "in" / u8"not_opaque_alpha.dds";
+
+    // Load.
+    auto opaque     = require_expected(btu::tex::load_crunch(opaque_file));
+    auto not_opaque = require_expected(btu::tex::load_crunch(not_opaque_file));
+
+    // Test alpha.
+    CHECK(opaque.has_opaque_alpha());
+    CHECK_FALSE(not_opaque.has_opaque_alpha());
+}
+
 TEST_CASE("Crunch resize", "[src]")
 {
     test_expected_dir_crunch(u8"crunch_resize", [](auto &&tex) {