photochk/Tests/PhotochkTests/TestImages.swift

import CoreGraphics
import Foundation
import ImageIO
import UniformTypeIdentifiers

/// テスト用の画像を決まった内容で作る。乱数は自前の線形合同法なので毎回同じ絵になる。
enum TestImages {
    static let width = 640
    static let height = 480

    struct Generator {
        private var state: UInt64

        init(seed: UInt64) { state = seed &* 2_862_933_555_777_941_757 &+ 3_037_000_493 }

        mutating func next() -> UInt64 {
            state = state &* 6_364_136_223_846_793_005 &+ 1_442_695_040_888_963_407
            return state
        }

        mutating func unit() -> Double {
            Double(next() >> 11) / Double(1 << 53)
        }
    }

    /// 色のついたブロックと円を敷き詰めた、構造のある絵を作る。
    static func pattern(seed: UInt64) -> CGImage {
        var generator = Generator(seed: seed)

        let context = CGContext(
            data: nil,
            width: width,
            height: height,
            bitsPerComponent: 8,
            bytesPerRow: 0,
            space: CGColorSpaceCreateDeviceRGB(),
            bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue
        )!

        let columns = 8
        let rows = 6
        let cellWidth = CGFloat(width) / CGFloat(columns)
        let cellHeight = CGFloat(height) / CGFloat(rows)

        for row in 0..<rows {
            for column in 0..<columns {
                context.setFillColor(
                    red: generator.unit(),
                    green: generator.unit(),
                    blue: generator.unit(),
                    alpha: 1
                )
                context.fill(
                    CGRect(
                        x: CGFloat(column) * cellWidth,
                        y: CGFloat(row) * cellHeight,
                        width: cellWidth,
                        height: cellHeight
                    )
                )
            }
        }

        for _ in 0..<12 {
            context.setFillColor(
                red: generator.unit(),
                green: generator.unit(),
                blue: generator.unit(),
                alpha: 0.85
            )
            let radius = 20 + generator.unit() * 60
            context.fillEllipse(
                in: CGRect(
                    x: generator.unit() * Double(width),
                    y: generator.unit() * Double(height),
                    width: radius,
                    height: radius
                )
            )
        }

        return context.makeImage()!
    }

    static func scaled(_ image: CGImage, factor: Double) -> CGImage {
        let newWidth = max(1, Int(Double(image.width) * factor))
        let newHeight = max(1, Int(Double(image.height) * factor))

        let context = CGContext(
            data: nil,
            width: newWidth,
            height: newHeight,
            bitsPerComponent: 8,
            bytesPerRow: 0,
            space: CGColorSpaceCreateDeviceRGB(),
            bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue
        )!
        context.interpolationQuality = .high
        context.draw(image, in: CGRect(x: 0, y: 0, width: newWidth, height: newHeight))
        return context.makeImage()!
    }

    static func writeJPEG(_ image: CGImage, to url: URL, quality: Double) throws {
        guard let destination = CGImageDestinationCreateWithURL(
            url as CFURL, UTType.jpeg.identifier as CFString, 1, nil
        ) else {
            throw TestImageError.cannotWrite(url)
        }
        CGImageDestinationAddImage(
            destination,
            image,
            [kCGImageDestinationLossyCompressionQuality: quality] as CFDictionary
        )
        guard CGImageDestinationFinalize(destination) else {
            throw TestImageError.cannotWrite(url)
        }
    }

    static func makeTemporaryDirectory() throws -> URL {
        let url = URL(fileURLWithPath: NSTemporaryDirectory())
            .appendingPathComponent("PhotochkTests-\(UUID().uuidString)", isDirectory: true)
        try FileManager.default.createDirectory(at: url, withIntermediateDirectories: true)
        return url
    }
}

enum TestImageError: Error {
    case cannotWrite(URL)
}