Swift CIKernel Plugin

The Swift CIKernel Plugin is a Swift Package Manager build tool plugin that builds Core Image Kernels into platform-specific Foundation.Data constants.

Unlike regular Metal sources, Core Image Kernels are built by passing the -fcikernel and -cikernel arguments to the Metal compiler and linker, respectively. This makes them a challenge to use in Swift Packages.

This plugin compiles Metal sources in your package target that follow the *Filter.metal naming convention into separate Metal libraries that then become available as constants of type Foundation.Data within your target.

For example, if your target includes a file named FalseColorFilter.metal, this will produce a constant named FalseColorFilterData that you can use from Swift as follows:

try CIKernel(functionName: "cdl", fromMetalLibraryData: FalseColorFilterData)

The filter is compiled separately for macOS (10.15+), iOS and tvOS (13+). FalseColorFilterData is conditionally defined for each of these platforms.

Usage

To use the Swift CIKernel Plugin with your package, first add it as a dependency:

// swift-tools-version:5.6

import PackageDescription

let package = Package(
    name: "ExamplePackage",
    platforms: [
        .macOS(.v10_15),
        .iOS(.v13),
        .tvOS(.v13),
    ],
    products: [
        .library(name: "ExampleLibrary", targets: ["ExampleTarget"]),
    ],
    dependencies: [
        .package(url: "https://github.com/in2core/swift-cikernel-plugin.git", from: "1.0.0"),
    ],
    targets: [
        .target(name: "ExampleTarget",
                // Exclude so that the default Metal compiler is not used.
                exclude: ["CIKernels"],
                plugins: [
                    .plugin(name: "Swift-CIKernel", package: "Swift-CIKernel-Plugin"),
                ]),
    ]
)

Notice that we exclude a folder named CIKernels from the target to prevent the default Metal compiler from being used. In this example, we would place our Core Image Kernels into the Sources/ExampleTarget/CIKernels directory. Alternatively, we could list the kernel source files one by one.

The test target in this package itself serves as an example of how this plugin is intended to be used.