ofxSkia

openFrameworks addon providing a Skia raster surface with ofTexture interop.

What it does

Wraps a Skia raster SkSurface so you can draw 2D vector graphics with SkCanvas, then blit the result to an ofTexture for display in an OF window. Skia handles anti-aliasing, path rendering, PDF export, and correct color space handling — none of which OF's built-in 2D API does well.

Classes

ofxSkiaSurface

The main entry point. Manages a raster surface, pixel readback, and texture upload.

ofxSkiaSurface surface;
surface.allocate(1280, 720);         // allocate at logical size
surface.allocate(1280, 720, 2.0f);   // with HiDPI scale factor

// draw frame
surface.begin();
SkCanvas* canvas = surface.getCanvas();
SkPaint paint;
paint.setColor(SK_ColorRED);
canvas->drawCircle(100, 100, 50, paint);
surface.end();

surface.updateTexture();             // blit pixels → ofTexture
surface.draw(0, 0);                  // render to OF window
surface.draw(0, 0, 640, 360);        // with explicit size

// introspection
surface.getWidth();
surface.getHeight();
surface.getScale();
surface.isAllocated();

ofxSkiaUtils.h

Inline conversion helpers between OF and Skia types. Include directly; no .cpp needed.

SkColor     ofColorToSk(const ofColor& c);
ofColor     skColorToOf(SkColor c);
SkRect      ofRectToSk(const ofRectangle& r);
ofRectangle skRectToOf(const SkRect& r);
SkPoint     ofVec2ToSk(const glm::vec2& v);

Building the library

Skia must be built from source once. The build takes ~30 minutes but the result is cached in libs/skia/.

# Fetch depot_tools + Skia source (~1 GB)
bash scripts/fetch_skia.sh

# Build (macOS universal: arm64 + x64)
bash scripts/build_skia_macos.sh

# Linux x64
bash scripts/build_skia_linux.sh

# Windows — run in PowerShell (requires depot_tools)
.\scripts\fetch_skia_windows.ps1
.\scripts\build_skia_windows.ps1

Output: libs/skia/lib/{osx,linux64,vs}/ + libs/skia/include/ + libs/skia/modules/skcms/
libs/ is git-ignored; run the scripts once per machine.

Skia build configuration (GN args)

Raster only — no GPU backend, no HarfBuzz/ICU duplication, PDF enabled:

is_debug=false
skia_use_gl=false  skia_use_metal=false  skia_use_vulkan=false
skia_enable_skparagraph=false  skia_enable_skshaper=false
skia_use_harfbuzz=false  skia_use_icu=false
skia_use_freetype=true  skia_use_system_freetype2=false
skia_enable_pdf=true

Important: SK_TRIVIAL_ABI

addon_config.mk sets -DSK_TRIVIAL_ABI=[[clang::trivial_abi]].
Without this, sk_sp<T> return values are passed incorrectly on ARM64 due to ABI mismatch between the Skia static lib and the caller.

CI

Skia is built from source on the first CI run and cached thereafter (libs/skia → actions/cache).

Platforms: macOS (Make + Xcode), Linux x64, Windows x64

Requirements

• openFrameworks 0.12.0+
• Skia chrome/m130
• macOS: Xcode CLI tools, brew install ninja
• Linux: ninja-build python3 libfontconfig1-dev libfreetype6-dev
• Windows: Visual Studio 2019+, Python 3, depot_tools

License

MIT