LibGfx: Implement YUV->RGBA color conversion for CPU painting

Using the Rust yuv crate, eagerly convert from YUV to RGBA on the CPU
when a GPU context is unavailable.

Time spent converting an 8-bit YUV frame with this crate is better than
libyuv on ARM by about 20%, and on x86 with AVX2, it achieves similar
numbers to libyuv.

Cargo.lock

@@ -361,6 +361,14 @@ version = "0.2.183"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b5b646652bf6661599e1da8901b3b9522896f01e736bad5f723fe7a3a27f899d"
 
+[[package]]
+name = "libgfx_rust"
+version = "0.1.0"
+dependencies = [
+ "cbindgen",
+ "yuv",
+]
+
 [[package]]
 name = "libjs_rust"
 version = "0.1.0"
@@ -892,6 +900,15 @@ dependencies = [
  "synstructure",
 ]
 
+[[package]]
+name = "yuv"
+version = "0.8.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47d3a7e2cda3061858987ee2fb028f61695f5ee13f9490d75be6c3900df9a4ea"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "zerofrom"
 version = "0.1.6"

Cargo.toml

@@ -1,5 +1,6 @@
 [workspace]
 members = [
+    "Libraries/LibGfx/Rust",
     "Libraries/LibJS/Rust",
     "Libraries/LibRegex/Rust",
     "Libraries/LibUnicode/Rust",

Libraries/LibGfx/CMakeLists.txt

@@ -118,6 +118,9 @@ find_package(harfbuzz REQUIRED)
 target_link_libraries(LibGfx PRIVATE PkgConfig::WOFF2 JPEG::JPEG PNG::PNG avif WebP::webp WebP::webpdecoder
             WebP::webpdemux WebP::libwebpmux skia harfbuzz)
 
+import_rust_crate(MANIFEST_PATH Rust/Cargo.toml CRATE_NAME libgfx_rust FFI_HEADER RustFFI.h)
+target_link_libraries(LibGfx PRIVATE libgfx_rust)
+
 if (HAS_FONTCONFIG)
     target_link_libraries(LibGfx PRIVATE Fontconfig::Fontconfig)
 endif()

Libraries/LibGfx/ImmutableBitmap.cpp

@@ -208,8 +208,10 @@ ErrorOr<NonnullRefPtr<ImmutableBitmap>> ImmutableBitmap::create_from_yuv(Nonnull
     auto context = SkiaBackendContext::the();
     auto* gr_context = context ? context->sk_context() : nullptr;
 
-    if (!gr_context)
-        return Error::from_string_literal("GPU context is unavailable");
+    if (!gr_context) {
+        auto bitmap = TRY(yuv_data->to_bitmap());
+        return create(move(bitmap), move(color_space));
+    }
 
     if (yuv_data->bit_depth() > 8)
         yuv_data->expand_samples_to_full_16_bit_range();

Libraries/LibGfx/Rust/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "libgfx_rust"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+crate-type = ["staticlib"]
+
+[dependencies]
+yuv = "0.8"
+
+[build-dependencies]
+cbindgen = "0.29"

Libraries/LibGfx/Rust/build.rs

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2026-present, the Ladybird developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+use std::env;
+use std::error::Error;
+use std::path::PathBuf;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR")?);
+    let out_dir = PathBuf::from(env::var("OUT_DIR")?);
+
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed=cbindgen.toml");
+    println!("cargo:rerun-if-env-changed=FFI_OUTPUT_DIR");
+    println!("cargo:rerun-if-changed=src");
+
+    let ffi_out_dir = env::var("FFI_OUTPUT_DIR")
+        .map(PathBuf::from)
+        .unwrap_or_else(|_| out_dir.clone());
+
+    cbindgen::generate(manifest_dir).map_or_else(
+        |error| match error {
+            cbindgen::Error::ParseSyntaxError { .. } => {}
+            e => panic!("{e:?}"),
+        },
+        |bindings| {
+            let header_path = out_dir.join("RustFFI.h");
+            bindings.write_to_file(&header_path);
+
+            if ffi_out_dir != out_dir {
+                bindings.write_to_file(ffi_out_dir.join("RustFFI.h"));
+            }
+        },
+    );
+
+    Ok(())
+}

Libraries/LibGfx/Rust/cbindgen.toml

@@ -0,0 +1,23 @@
+language = "C++"
+header = """/*
+ * Copyright (c) 2026-present, the Ladybird developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */"""
+pragma_once = true
+include_version = true
+line_length = 120
+tab_width = 4
+no_includes = true
+sys_includes = ["stdint.h", "stddef.h"]
+usize_is_size_t = true
+namespaces = ["Gfx", "FFI"]
+
+[parse]
+parse_deps = false
+
+[parse.expand]
+all_features = false
+
+[export.mangle]
+rename_types = "PascalCase"

Libraries/LibGfx/Rust/src/lib.rs

@@ -0,0 +1,241 @@
+/*
+ * Copyright (c) 2026-present, the Ladybird developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+use yuv::{YuvPlanarImage, YuvRange, YuvStandardMatrix};
+
+#[repr(u8)]
+pub enum YUVRange {
+    Limited = 0,
+    Full = 1,
+}
+
+#[repr(u8)]
+pub enum YUVMatrix {
+    Bt709 = 0,
+    Fcc = 1,
+    Bt470BG = 2,
+    Bt601 = 3,
+    Smpte240 = 4,
+    Bt2020 = 5,
+}
+
+impl From<YUVRange> for YuvRange {
+    fn from(range: YUVRange) -> Self {
+        match range {
+            YUVRange::Limited => YuvRange::Limited,
+            YUVRange::Full => YuvRange::Full,
+        }
+    }
+}
+
+impl From<YUVMatrix> for YuvStandardMatrix {
+    fn from(matrix: YUVMatrix) -> Self {
+        match matrix {
+            YUVMatrix::Bt709 => YuvStandardMatrix::Bt709,
+            YUVMatrix::Fcc => YuvStandardMatrix::Fcc,
+            YUVMatrix::Bt470BG => YuvStandardMatrix::Bt470_6,
+            YUVMatrix::Bt601 => YuvStandardMatrix::Bt601,
+            YUVMatrix::Smpte240 => YuvStandardMatrix::Smpte240,
+            YUVMatrix::Bt2020 => YuvStandardMatrix::Bt2020,
+        }
+    }
+}
+
+/// # Safety
+/// All plane pointers must be valid for the specified dimensions and strides.
+/// `dst` must point to a buffer of at least `dst_stride * height` bytes.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn yuv_u8_to_rgba(
+    y_plane: *const u8,
+    y_stride: u32,
+    u_plane: *const u8,
+    u_stride: u32,
+    v_plane: *const u8,
+    v_stride: u32,
+    width: u32,
+    height: u32,
+    subsampling_x: bool,
+    subsampling_y: bool,
+    dst: *mut u8,
+    dst_stride: u32,
+    range: YUVRange,
+    matrix: YUVMatrix,
+) -> bool {
+    let y_len = y_stride as usize * height as usize;
+    let uv_height = if subsampling_y {
+        height.div_ceil(2)
+    } else {
+        height
+    } as usize;
+    let uv_len = u_stride as usize * uv_height;
+
+    let planar_image = YuvPlanarImage {
+        y_plane: unsafe { core::slice::from_raw_parts(y_plane, y_len) },
+        y_stride,
+        u_plane: unsafe { core::slice::from_raw_parts(u_plane, uv_len) },
+        u_stride,
+        v_plane: unsafe { core::slice::from_raw_parts(v_plane, uv_len) },
+        v_stride,
+        width,
+        height,
+    };
+
+    let dst_len = dst_stride as usize * height as usize;
+    let dst_slice = unsafe { core::slice::from_raw_parts_mut(dst, dst_len) };
+
+    let result = match (subsampling_x, subsampling_y) {
+        (true, true) => yuv::yuv420_to_rgba(
+            &planar_image,
+            dst_slice,
+            dst_stride,
+            range.into(),
+            matrix.into(),
+        ),
+        (true, false) => yuv::yuv422_to_rgba(
+            &planar_image,
+            dst_slice,
+            dst_stride,
+            range.into(),
+            matrix.into(),
+        ),
+        (false, true) => return false,
+        (false, false) => yuv::yuv444_to_rgba(
+            &planar_image,
+            dst_slice,
+            dst_stride,
+            range.into(),
+            matrix.into(),
+        ),
+    };
+
+    result.is_ok()
+}
+
+/// # Safety
+/// All plane pointers must be valid for the specified dimensions and strides.
+/// `dst` must point to a buffer of at least `dst_stride * height` bytes.
+/// Values in the u16 planes must be in 0-1023 range for 10-bit or 0-4095 for 12-bit.
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn yuv_u16_to_rgba(
+    y_plane: *const u16,
+    y_stride: u32,
+    u_plane: *const u16,
+    u_stride: u32,
+    v_plane: *const u16,
+    v_stride: u32,
+    width: u32,
+    height: u32,
+    bit_depth: u8,
+    subsampling_x: bool,
+    subsampling_y: bool,
+    dst: *mut u8,
+    dst_stride: u32,
+    range: YUVRange,
+    matrix: YUVMatrix,
+) -> bool {
+    let y_len = y_stride as usize * height as usize;
+    let uv_height = if subsampling_y {
+        height.div_ceil(2)
+    } else {
+        height
+    } as usize;
+    let uv_len = u_stride as usize * uv_height;
+
+    let planar_image = YuvPlanarImage {
+        y_plane: unsafe { core::slice::from_raw_parts(y_plane, y_len) },
+        y_stride,
+        u_plane: unsafe { core::slice::from_raw_parts(u_plane, uv_len) },
+        u_stride,
+        v_plane: unsafe { core::slice::from_raw_parts(v_plane, uv_len) },
+        v_stride,
+        width,
+        height,
+    };
+
+    let dst_len = dst_stride as usize * height as usize;
+    let dst_slice = unsafe { core::slice::from_raw_parts_mut(dst, dst_len) };
+
+    let result = if bit_depth <= 10 {
+        match (subsampling_x, subsampling_y) {
+            (true, true) => yuv::i010_to_rgba(
+                &planar_image,
+                dst_slice,
+                dst_stride,
+                range.into(),
+                matrix.into(),
+            ),
+            (true, false) => yuv::i210_to_rgba(
+                &planar_image,
+                dst_slice,
+                dst_stride,
+                range.into(),
+                matrix.into(),
+            ),
+            (false, true) => return false,
+            (false, false) => yuv::i410_to_rgba(
+                &planar_image,
+                dst_slice,
+                dst_stride,
+                range.into(),
+                matrix.into(),
+            ),
+        }
+    } else {
+        // 12-bit 4:4:4 has no 8-bit RGBA output; shift to 10-bit and use I410.
+        if !subsampling_x && !subsampling_y {
+            let y_10: Vec<u16> = unsafe { core::slice::from_raw_parts(y_plane, y_len) }
+                .iter()
+                .map(|&v| v >> 2)
+                .collect();
+            let u_10: Vec<u16> = unsafe { core::slice::from_raw_parts(u_plane, uv_len) }
+                .iter()
+                .map(|&v| v >> 2)
+                .collect();
+            let v_10: Vec<u16> = unsafe { core::slice::from_raw_parts(v_plane, uv_len) }
+                .iter()
+                .map(|&v| v >> 2)
+                .collect();
+            let planar_10 = YuvPlanarImage {
+                y_plane: &y_10,
+                y_stride,
+                u_plane: &u_10,
+                u_stride,
+                v_plane: &v_10,
+                v_stride,
+                width,
+                height,
+            };
+            return yuv::i410_to_rgba(
+                &planar_10,
+                dst_slice,
+                dst_stride,
+                range.into(),
+                matrix.into(),
+            )
+            .is_ok();
+        }
+        match (subsampling_x, subsampling_y) {
+            (true, true) => yuv::i012_to_rgba(
+                &planar_image,
+                dst_slice,
+                dst_stride,
+                range.into(),
+                matrix.into(),
+            ),
+            (true, false) => yuv::i212_to_rgba(
+                &planar_image,
+                dst_slice,
+                dst_stride,
+                range.into(),
+                matrix.into(),
+            ),
+            (false, true) => return false,
+            (false, false) => unreachable!(),
+        }
+    };
+
+    result.is_ok()
+}

Libraries/LibGfx/YUVData.cpp

@@ -4,9 +4,12 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Time.h>
+#include <LibGfx/Bitmap.h>
 #include <LibGfx/ImmutableBitmap.h>
 #include <LibGfx/SkiaBackendContext.h>
 #include <LibGfx/YUVData.h>
+#include <RustFFI.h>
 
 #include <core/SkColorSpace.h>
 #include <core/SkImage.h>
@@ -102,6 +105,126 @@ Bytes YUVData::v_data()
     return m_impl->v_buffer.span();
 }
 
+static FFI::YUVMatrix yuv_matrix_for_cicp(Media::CodingIndependentCodePoints const& cicp)
+{
+    switch (cicp.matrix_coefficients()) {
+    case Media::MatrixCoefficients::Identity:
+        VERIFY_NOT_REACHED();
+    case Media::MatrixCoefficients::FCC:
+        return FFI::YUVMatrix::Fcc;
+    case Media::MatrixCoefficients::BT470BG:
+        return FFI::YUVMatrix::Bt470BG;
+    case Media::MatrixCoefficients::BT601:
+        return FFI::YUVMatrix::Bt601;
+    case Media::MatrixCoefficients::SMPTE240:
+        return FFI::YUVMatrix::Smpte240;
+    case Media::MatrixCoefficients::BT2020NonConstantLuminance:
+    case Media::MatrixCoefficients::BT2020ConstantLuminance:
+        return FFI::YUVMatrix::Bt2020;
+    case Media::MatrixCoefficients::BT709:
+    case Media::MatrixCoefficients::Unspecified:
+    default:
+        return FFI::YUVMatrix::Bt709;
+    }
+}
+
+ErrorOr<NonnullRefPtr<Bitmap>> YUVData::to_bitmap() const
+{
+    auto const& impl = *m_impl;
+    VERIFY(impl.bit_depth <= 12);
+
+    auto bitmap = TRY(Bitmap::create(BitmapFormat::RGBA8888, AlphaType::Premultiplied, impl.size));
+    auto* dst = reinterpret_cast<u8*>(bitmap->scanline(0));
+    auto dst_stride = static_cast<u32>(bitmap->pitch());
+
+    auto width = static_cast<u32>(impl.size.width());
+    auto height = static_cast<u32>(impl.size.height());
+
+    if (impl.cicp.matrix_coefficients() == Media::MatrixCoefficients::Identity) {
+        if (impl.subsampling.x() || impl.subsampling.y())
+            return Error::from_string_literal("Subsampled RGB is unsupported");
+
+        if (impl.bit_depth <= 8) {
+            auto const* y_data = impl.y_buffer.data();
+            auto const* u_data = impl.u_buffer.data();
+            auto const* v_data = impl.v_buffer.data();
+            auto y_stride = static_cast<int>(width);
+
+            for (u32 row = 0; row < height; row++) {
+                auto* dst_row = dst + (static_cast<size_t>(row) * dst_stride);
+                auto const* y_row = y_data + (static_cast<size_t>(row) * y_stride);
+                auto const* u_row = u_data + (static_cast<size_t>(row) * y_stride);
+                auto const* v_row = v_data + (static_cast<size_t>(row) * y_stride);
+                for (u32 col = 0; col < width; col++) {
+                    dst_row[(col * 4) + 0] = v_row[col];
+                    dst_row[(col * 4) + 1] = y_row[col];
+                    dst_row[(col * 4) + 2] = u_row[col];
+                    dst_row[(col * 4) + 3] = 255;
+                }
+            }
+        } else {
+            // Our buffers hold native N-bit values in the low bits of each u16; shift right to reduce
+            // to 8-bit for the output.
+            auto shift = impl.bit_depth - 8;
+            auto const* y_data = reinterpret_cast<u16 const*>(impl.y_buffer.data());
+            auto const* u_data = reinterpret_cast<u16 const*>(impl.u_buffer.data());
+            auto const* v_data = reinterpret_cast<u16 const*>(impl.v_buffer.data());
+            auto y_stride = static_cast<int>(width);
+
+            for (u32 row = 0; row < height; row++) {
+                auto* dst_row = dst + (static_cast<size_t>(row) * dst_stride);
+                auto const* y_row = y_data + (static_cast<size_t>(row) * y_stride);
+                auto const* u_row = u_data + (static_cast<size_t>(row) * y_stride);
+                auto const* v_row = v_data + (static_cast<size_t>(row) * y_stride);
+                for (u32 col = 0; col < width; col++) {
+                    dst_row[(col * 4) + 0] = static_cast<u8>(v_row[col] >> shift);
+                    dst_row[(col * 4) + 1] = static_cast<u8>(y_row[col] >> shift);
+                    dst_row[(col * 4) + 2] = static_cast<u8>(u_row[col] >> shift);
+                    dst_row[(col * 4) + 3] = 255;
+                }
+            }
+        }
+
+        return bitmap;
+    }
+
+    auto uv_size = impl.subsampling.subsampled_size(impl.size).to_type<u32>();
+
+    bool full_range = impl.cicp.video_full_range_flag() == Media::VideoFullRangeFlag::Full;
+    auto range = full_range ? FFI::YUVRange::Full : FFI::YUVRange::Limited;
+    auto matrix = yuv_matrix_for_cicp(impl.cicp);
+
+    auto y_stride = width;
+    auto uv_stride = uv_size.width();
+
+    bool success;
+    if (impl.bit_depth <= 8) {
+        success = FFI::yuv_u8_to_rgba(
+            impl.y_buffer.data(), y_stride,
+            impl.u_buffer.data(), uv_stride,
+            impl.v_buffer.data(), uv_stride,
+            width, height,
+            impl.subsampling.x(), impl.subsampling.y(),
+            dst, dst_stride,
+            range, matrix);
+    } else {
+        success = FFI::yuv_u16_to_rgba(
+            reinterpret_cast<u16 const*>(impl.y_buffer.data()), y_stride,
+            reinterpret_cast<u16 const*>(impl.u_buffer.data()), uv_stride,
+            reinterpret_cast<u16 const*>(impl.v_buffer.data()), uv_stride,
+            width, height,
+            impl.bit_depth,
+            impl.subsampling.x(), impl.subsampling.y(),
+            dst, dst_stride,
+            range, matrix);
+    }
+
+    if (!success)
+        return Error::from_string_literal("YUV-to-RGB conversion failed");
+
+    return bitmap;
+}
+
 void YUVData::expand_samples_to_full_16_bit_range()
 {
     auto const shift = 16 - m_impl->bit_depth;

Libraries/LibGfx/YUVData.h

@@ -9,6 +9,8 @@
 #include <AK/Error.h>
 #include <AK/FixedArray.h>
 #include <AK/NonnullOwnPtr.h>
+#include <AK/NonnullRefPtr.h>
+#include <LibGfx/Forward.h>
 #include <LibGfx/Size.h>
 #include <LibMedia/Color/CodingIndependentCodePoints.h>
 #include <LibMedia/Subsampling.h>
@@ -42,6 +44,8 @@ public:
     Bytes u_data();
     Bytes v_data();
 
+    ErrorOr<NonnullRefPtr<Bitmap>> to_bitmap() const;
+
     SkYUVAPixmaps make_pixmaps() const;
 
     void expand_samples_to_full_16_bit_range();

Meta/CMake/flatpak/cargo-sources.json

@@ -656,6 +656,13 @@
         "sha256": "de844c262c8848816172cef550288e7dc6c7b7814b4ee56b3e1553f275f1858e",
         "dest": "cargo/vendor/yoke-derive-0.8.2"
     },
+    {
+        "type": "archive",
+        "archive-type": "tar-gzip",
+        "url": "https://static.crates.io/crates/yuv/yuv-0.8.13.crate",
+        "sha256": "47d3a7e2cda3061858987ee2fb028f61695f5ee13f9490d75be6c3900df9a4ea",
+        "dest": "cargo/vendor/yuv-0.8.13"
+    },
     {
         "type": "archive",
         "archive-type": "tar-gzip",
@@ -794,6 +801,7 @@
             "echo '{\"files\": {}, \"package\": \"9edde0db4769d2dc68579893f2306b26c6ecfbe0ef499b013d731b7b9247e0b9\"}' > cargo/vendor/writeable-0.6.2/.cargo-checksum.json",
             "echo '{\"files\": {}, \"package\": \"abe8c5fda708d9ca3df187cae8bfb9ceda00dd96231bed36e445a1a48e66f9ca\"}' > cargo/vendor/yoke-0.8.2/.cargo-checksum.json",
             "echo '{\"files\": {}, \"package\": \"de844c262c8848816172cef550288e7dc6c7b7814b4ee56b3e1553f275f1858e\"}' > cargo/vendor/yoke-derive-0.8.2/.cargo-checksum.json",
+            "echo '{\"files\": {}, \"package\": \"47d3a7e2cda3061858987ee2fb028f61695f5ee13f9490d75be6c3900df9a4ea\"}' > cargo/vendor/yuv-0.8.13/.cargo-checksum.json",
             "echo '{\"files\": {}, \"package\": \"50cc42e0333e05660c3587f3bf9d0478688e15d870fab3346451ce7f8c9fbea5\"}' > cargo/vendor/zerofrom-0.1.6/.cargo-checksum.json",
             "echo '{\"files\": {}, \"package\": \"d71e5d6e06ab090c67b5e44993ec16b72dcbaabc526db883a360057678b48502\"}' > cargo/vendor/zerofrom-derive-0.1.6/.cargo-checksum.json",
             "echo '{\"files\": {}, \"package\": \"0f9152d31db0792fa83f70fb2f83148effb5c1f5b8c7686c3459e361d9bc20bf\"}' > cargo/vendor/zerotrie-0.2.4/.cargo-checksum.json",