Skia Go Package

A Go port of Skia's core drawing primitives, designed to be backend-agnostic, Bring Your Own Graphics Backend.

Overview

This package provides a complete implementation of Skia's fundamental graphics types and operations in pure Go. It follows Skia's C++ API closely while adapting to Go idioms and conventions.

Package Structure

base/

Core foundational types and constants:

• Scalar: Floating-point type (float32) used throughout the package
• Constants: Matrix indices, segment masks, and mathematical constants

interfaces/

Interface definitions for all major graphics primitives:

• SkPaint: Paint interface for specifying how geometry is drawn (color, stroke, blend modes, filters)
• SkPath: Path interface for creating and manipulating 2D paths
• SkMatrix: Matrix interface for 2D transformations
• Filter Interfaces: Shader, ColorFilter, ImageFilter, MaskFilter, PathEffect, Blender

models/

Data structures representing geometric and color primitives:

• Point: 2D point with X, Y coordinates
• Rect: Rectangle with Left, Top, Right, Bottom bounds
• RRect: Rounded rectangle with corner radii
• Color4f: RGBA color with float components (unpremultiplied)

enums/

Enumerations for various graphics operations:

• BlendMode: Porter-Duff and advanced blend modes (SrcOver, Multiply, Screen, etc.)
• PaintStyle: Fill, Stroke, or StrokeAndFill
• PaintCap: Stroke cap styles (Butt, Round, Square)
• PaintJoin: Stroke join styles (Miter, Round, Bevel)
• PathFillType: Fill rules (Winding, EvenOdd, Inverse variants)
• PathVerb: Path commands (Move, Line, Quad, Conic, Cubic, Close)
• PathDirection: Contour direction (CW, CCW)
• PathConvexity: Path convexity classification
• MatrixType: Matrix classification flags

geometry/

Geometric primitives and utilities:

• Conic: Conic section curves for accurate path rendering
• Helpers: Geometric algorithms and utility functions

impl/

Concrete implementations of the interfaces:

• Paint: Complete paint implementation with:
  • Color management (RGBA, ARGB, alpha)
  • Stroke properties (width, cap, join, miter limit)
  • Blend modes and custom blenders
  • Filter support (shader, color filter, image filter, mask filter, path effect)
  • Fast bounds computation
• Path: Complete path implementation with:
  • Verb-based path construction (MoveTo, LineTo, QuadTo, ConicTo, CubicTo, Close)
  • Path manipulation (Transform, Offset, AddPath)
  • Bounds computation (bounds, tight bounds)
  • Convexity detection
  • Fill type management
• Matrix: 3x3 transformation matrix with:
  • Affine transformations (translate, scale, rotate, skew)
  • Perspective transformations
  • Point and rect mapping
  • Matrix concatenation (pre/post)

paragraph/

Advanced text layout engine (port of SkParagraph):

• Paragraph: High-level text layout and rendering
• Builder: Fluent builder pattern for creating paragraphs
• Styling: Rich text styling (TextStyle, ParagraphStyle)
• Types: Layout primitives (TextBox, Position, Range)

shaper/

Text shaping and processing:

• Shaper: Interface for text shaping engines
• HarfBuzz: Production-grade shaping using HarfBuzz
• Script & Bidi: Script detection and bidirectional text analysis
• Font Management: Font fallback and collection handling

helpers/

Utility functions for mathematical operations:

• CrossProduct: 2D cross product
• DotProduct: 2D dot product
• Sign: Sign function
• ScalarPin: Clamp scalar values

Key Features

• Backend Agnostic: Interfaces allow different backends (OpenGL, Vulkan, Metal, CPU) to implement rendering
• Complete Paint System: Full support for colors, strokes, blend modes, and all filter types
• Robust Path Implementation: Verb-based path system with proper bounds and convexity tracking
• Matrix Transformations: Full 3x3 matrix support including perspective
• Type Safety: Strong typing throughout with clear separation of concerns

Usage Example

import (
    "github.com/zodimo/go-skia-support/skia/interfaces"
    "github.com/zodimo/go-skia-support/skia/impl"
    "github.com/zodimo/go-skia-support/skia/models"
    "github.com/zodimo/go-skia-support/skia/enums"
)

// Create a paint
paint := impl.NewPaint()
paint.SetColor(models.Color4f{R: 1.0, G: 0.0, B: 0.0, A: 1.0})
paint.SetStyle(enums.PaintStyleFill)
paint.SetAntiAlias(true)

// Create a path
path := impl.NewSkPath(enums.PathFillTypeWinding)
path.AddCircle(100, 100, 50, enums.PathDirectionCW)

// Create a matrix
matrix := impl.NewMatrixTranslate(10, 20)

Development Status

Skia version : release chrome/m144

The implementation aims to follow Skia's C++ codebase closely and is designed to be a drop-in replacement for Skia's core types in Go applications.