OpenCoreGraphics

A Swift library that provides full API compatibility with Apple's CoreGraphics framework for WebAssembly (WASM) environments.

Overview

OpenCoreGraphics enables cross-platform Swift code to use CoreGraphics APIs in WASM environments where Apple's CoreGraphics is not available. The API is designed to be 100% compatible with CoreGraphics, allowing code to compile and work without modification.

Installation

Add OpenCoreGraphics to your Package.swift:

dependencies: [
    .package(url: "https://github.com/1amageek/OpenCoreGraphics.git", from: "1.0.0")
]

Then add it to your target:

.target(
    name: "YourTarget",
    dependencies: ["OpenCoreGraphics"]
)

Usage

Use conditional imports to support both Apple platforms and WASM:

#if canImport(CoreGraphics)
import CoreGraphics
#else
import OpenCoreGraphics
#endif

Drawing with CGContext

// Create a bitmap context
let context = CGContext(
    data: nil,
    width: 400,
    height: 300,
    bitsPerComponent: 8,
    bytesPerRow: 400 * 4,
    space: CGColorSpace(name: CGColorSpace.sRGB)!,
    bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
)!

// Draw shapes
context.setFillColor(CGColor(red: 1, green: 0, blue: 0, alpha: 1))
context.fill(CGRect(x: 50, y: 50, width: 100, height: 80))

context.setStrokeColor(CGColor(red: 0, green: 0, blue: 1, alpha: 1))
context.setLineWidth(3)
context.strokeEllipse(in: CGRect(x: 200, y: 50, width: 100, height: 100))

// Get the rendered image
let image = context.makeImage()

Path Drawing

let path = CGMutablePath()
path.move(to: CGPoint(x: 100, y: 100))
path.addLine(to: CGPoint(x: 200, y: 100))
path.addLine(to: CGPoint(x: 150, y: 200))
path.closeSubpath()

context.addPath(path)
context.setFillColor(.red)
context.fillPath()

Gradients

let gradient = CGGradient(
    colorsSpace: CGColorSpace(name: CGColorSpace.sRGB)!,
    colors: [CGColor.red, CGColor.blue],
    locations: [0, 1]
)!

context.drawLinearGradient(
    gradient,
    start: CGPoint(x: 0, y: 0),
    end: CGPoint(x: 400, y: 300),
    options: []
)

Transforms

context.saveGState()
context.translateBy(x: 200, y: 150)
context.rotate(by: .pi / 4)
context.scaleBy(x: 2, y: 2)
context.fill(CGRect(x: -25, y: -25, width: 50, height: 50))
context.restoreGState()

WASM Usage

On WASM, OpenCoreGraphics uses WebGPU for hardware-accelerated rendering. Call setupGraphicsContext() once at application startup to initialize WebGPU.

import OpenCoreGraphics

@main
struct MyApp {
    static func main() async throws {
        // Initialize WebGPU (call once at startup)
        try await setupGraphicsContext()

        // Now use CGContext normally
        let context = CGContext(
            data: nil,
            width: 400,
            height: 300,
            bitsPerComponent: 8,
            bytesPerRow: 400 * 4,
            space: CGColorSpace(name: CGColorSpace.sRGB)!,
            bitmapInfo: CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
        )!

        context.setFillColor(CGColor(red: 1, green: 0, blue: 0, alpha: 1))
        context.fill(CGRect(x: 0, y: 0, width: 100, height: 100))

        // GPU readback
        let image = await context.makeImageAsync()
    }
}

Error Handling

setupGraphicsContext() throws GraphicsContextError if initialization fails:

do {
    try await setupGraphicsContext()
} catch GraphicsContextError.webGPUNotSupported {
    // Browser doesn't support WebGPU
} catch GraphicsContextError.adapterNotAvailable {
    // Failed to get WebGPU adapter
} catch GraphicsContextError.deviceNotAvailable {
    // Failed to get WebGPU device
}

Browser Requirements

WebGPU is required for WASM rendering. Supported browsers:

Chrome 113+
Edge 113+
Firefox 139+ (with flags)
Safari 18+ (macOS Sequoia / iOS 18)

Implemented Types

Geometric Data Types

CGFloat, CGPoint, CGSize, CGRect, CGVector
CGAffineTransform, CGAffineTransformComponents

2D Drawing

CGContext, CGImage, CGPath, CGMutablePath, CGLayer

Colors & Color Spaces

CGColor, CGColorSpace, CGColorSpaceModel, CGColorConversionInfo
CGComponent, CGBitmapInfo, CGImageAlphaInfo

Gradients & Patterns

CGGradient, CGShading, CGPattern, CGFunction

Data Handling

CGDataProvider, CGDataConsumer

PDF Support

CGPDFDocument, CGPDFPage, CGPDFObject, CGPDFScanner

Fonts

CGFont

Enums & Options

CGBlendMode, CGTextDrawingMode, CGInterpolationQuality
CGGradientDrawingOptions, CGPathFillRule, CGLineCap, CGLineJoin
And more...

Building

# Build the package
swift build

# Run tests
swift test

# Build for WASM (requires Swift SDK for WASM)
swift build --swift-sdk <your-wasm-sdk>

# Example with specific SDK
swift build --swift-sdk swift-6.2.3-RELEASE_wasm

Installing Swift WASM SDK

# Install the Swift WASM SDK
swift sdk install https://github.com/aspect-build/aspect-wasm32-wasi-release/releases/latest/download/swift-wasm32-wasi.artifactbundle.zip

# List installed SDKs
swift sdk list

Requirements

Swift 6.0+
For WASM builds: Swift WASM SDK

WASM Compatibility

This library is designed with WASM compatibility as a primary goal. All implementations use pure Swift types that work seamlessly in WebAssembly environments.

Pure Swift Implementation

OpenCoreGraphics is built entirely with Swift standard types:

String for names and identifiers
Data for binary data
[String: Any] for property lists and dictionaries
UInt for type identifiers

Supported Color Spaces

All standard color space names are available as String constants:

CGColorSpace.sRGB                    // "kCGColorSpaceSRGB"
CGColorSpace.displayP3               // "kCGColorSpaceDisplayP3"
CGColorSpace.genericGrayGamma2_2     // "kCGColorSpaceGenericGrayGamma2_2"
CGColorSpace.genericCMYK             // "kCGColorSpaceGenericCMYK"
// ... and many more

Design Principles

Full API Compatibility: Identical type names, method signatures, and property names as CoreGraphics
WASM First: Uses pure Swift types that work in WebAssembly environments
Same Behavior: Consistent semantics with Apple's implementation
Modern Swift: All value types are @frozen and conform to Sendable, Hashable, Equatable, and Codable
No Deprecated APIs: Only current, non-deprecated CoreGraphics APIs are implemented
Performance Optimized: Uses @inlinable for performance-critical methods

Protocol Conformances

All geometric value types (CGFloat, CGPoint, CGSize, CGRect, CGVector, CGAffineTransform) conform to:

Sendable - Thread-safe
Hashable - Can be used in Sets and as Dictionary keys
Equatable - Equality comparison
Codable - JSON serialization support

Additionally, CGFloat conforms to all numeric protocols:

FloatingPoint, BinaryFloatingPoint
SignedNumeric, Numeric
Comparable, Strideable

License

MIT License