Using private CIInpaintingFilter on macOS to recreate Photos "Clean up" feature

cleanup.swift

import Foundation
import CoreImage

struct CleanupError: LocalizedError {
    let message: String
    var errorDescription: String? { message }
}

/// Remove a rectangle using the OS inpainting model. Rect uses whole pixels from the top-left of the oriented image.
public func cleanUp(_ image: CIImage, rect: CGRect) throws -> CIImage {
    let source = image.transformed(by: .init(translationX: -image.extent.minX, y: -image.extent.minY))
    guard rect.width > 0, rect.height > 0, rect == rect.integral, source.extent.contains(rect) else {
        throw CleanupError(message: "The rectangle must use whole pixels and fit inside the image.")
    }
    guard let filter = CIFilter(name: "CIInpaintingFilter") else {
        throw CleanupError(message: "This OS does not provide the inpainting filter.")
    }
    let area = CGRect(x: rect.minX, y: source.extent.height - rect.maxY, width: rect.width, height: rect.height)
    let mask = CIImage(color: .white).cropped(to: area).composited(over: CIImage(color: .black).cropped(to: source.extent))
    filter.setValue(source, forKey: kCIInputImageKey)
    // The inpainting filter removes black pixels; the blend mask uses white.
    filter.setValue(mask.applyingFilter("CIColorInvert"), forKey: kCIInputMaskImageKey)
    filter.setValue(CIVector(cgRect: area), forKey: "inputMaskBoundingBox")
    guard let generated = filter.outputImage else {
        throw CleanupError(message: "The inpainting filter did not return an image.")
    }
    return generated.applyingFilter("CIBlendWithMask", parameters: [kCIInputBackgroundImageKey: source, kCIInputMaskImageKey: mask]).cropped(to: source.extent)
}

main.swift

import Foundation
import CoreImage

do {
    let args = CommandLine.arguments
    guard args.count == 6 || args.count == 7 else {
        throw CleanupError(message: "Usage: cleanup-image INPUT X Y WIDTH HEIGHT [OUTPUT.png]")
    }
    let values = args[2...5].compactMap(Int.init)
    guard values.count == 4 else {
        throw CleanupError(message: "X, Y, WIDTH and HEIGHT must be integers in pixels.")
    }
    let inputURL = URL(fileURLWithPath: args[1])
    let outputURL = args.count == 7 ? URL(fileURLWithPath: args[6]) : inputURL.deletingPathExtension().appendingPathExtension("cleaned.png")
    guard !FileManager.default.fileExists(atPath: outputURL.path) else {
        throw CleanupError(message: "The output already exists. Choose a new output path.")
    }
    guard let source = CIImage(contentsOf: inputURL, options: [.applyOrientationProperty: true]) else {
        throw CleanupError(message: "Core Image cannot read the input image.")
    }
    let rect = CGRect(x: values[0], y: values[1], width: values[2], height: values[3])
    let result = try cleanUp(source, rect: rect)
    try CIContext().writePNGRepresentation(of: result, to: outputURL, format: .RGBA8, colorSpace: CGColorSpace(name: CGColorSpace.sRGB)!)
    print(outputURL.path)
} catch {
    FileHandle.standardError.write(Data("\(error.localizedDescription)\n".utf8))
    exit(1)
}