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import AppKit
import ArgumentParser
import Compute
import Metal
@main
struct PixelSort: ParsableCommand {
static let configuration = CommandConfiguration(
abstract: "Metal-accelerated pixel sorting library"
)
@Argument(help: "Input image path")
var input: String
@Argument(help: "Output image path")
var output: String
@Option(name: .shortAndLong, help: "Sort key: brightness, hue, saturation, R, G, B")
var key: SortKeyOption = .brightness
@Option(name: .shortAndLong, help: "Lower brightness threshold (0.0–1.0)")
var lower: Float = 0.1
@Option(name: .shortAndLong, help: "Upper brightness threshold (0.0–1.0)")
var upper: Float = 0.9
@Flag(name: .shortAndLong, help: "Sort descending (reverse)")
var descending: Bool = false
@Option(name: .shortAndLong, help: "Gamma applied to sorted pixels (Unity-style composite)")
var gamma: Float = 1.0
@Option(name: .shortAndLong, help: "Clamp maximum sortable span length (default: image width)")
var maxSpan: Int?
@Flag(name: .long, help: "Invert the threshold mask")
var invertMask: Bool = false
mutating func run() throws {
let device = MTLCreateSystemDefaultDevice()!
let compute = try Compute(device: device)
let inputURL = URL(fileURLWithPath: input)
let outputURL = URL(fileURLWithPath: self.output)
guard let nsImage = NSImage(contentsOf: inputURL),
let cgImage = nsImage.cgImage(forProposedRect: nil, context: nil, hints: nil)
else {
throw ValidationError("Could not load image")
}
let width = cgImage.width
let height = cgImage.height
let rgbaDesc = MTLTextureDescriptor.texture2DDescriptor(
pixelFormat: .rgba8Unorm,
width: width,
height: height,
mipmapped: false
)
rgbaDesc.usage = [.shaderRead, .shaderWrite]
let texA = device.makeTexture(descriptor: rgbaDesc)!
let texB = device.makeTexture(descriptor: rgbaDesc)!
texA.label = "original"
texB.label = "output"
let sortedTex = device.makeTexture(descriptor: rgbaDesc)!
sortedTex.label = "sorted"
let maskDesc = MTLTextureDescriptor.texture2DDescriptor(
pixelFormat: .r8Uint,
width: width,
height: height,
mipmapped: false
)
maskDesc.usage = [.shaderRead, .shaderWrite]
let maskTex = device.makeTexture(descriptor: maskDesc)!
maskTex.label = "mask"
let spanDesc = MTLTextureDescriptor.texture2DDescriptor(
pixelFormat: .r32Uint,
width: width,
height: height,
mipmapped: false
)
spanDesc.usage = [.shaderRead, .shaderWrite]
let spanTex = device.makeTexture(descriptor: spanDesc)!
spanTex.label = "spans"
let bytesPerPixel = 4
let bytesPerRow = bytesPerPixel * width
var pixelData = [UInt8](repeating: 0, count: width * height * bytesPerPixel)
let colorSpace = CGColorSpaceCreateDeviceRGB()
guard
let ctx = CGContext(
data: &pixelData,
width: width,
height: height,
bitsPerComponent: 8,
bytesPerRow: bytesPerRow,
space: colorSpace,
bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
)
else {
throw ValidationError("Failed to create CGContext")
}
ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))
texA.replace(
region: MTLRegionMake2D(0, 0, width, height),
mipmapLevel: 0,
withBytes: pixelData,
bytesPerRow: bytesPerRow
)
let shaderSource = try String(
contentsOf: Bundle.module.url(forResource: "Shaders", withExtension: "metal")!,
encoding: .utf8)
let library = ShaderLibrary.source(shaderSource)
var createMaskPipeline = try compute.makePipeline(function: library.createMask)
var clearSpanPipeline = try compute.makePipeline(function: library.clearSpanBuffer)
var identifySpansPipeline = try compute.makePipeline(function: library.identifySpans)
var pixelSortPipeline = try compute.makePipeline(function: library.pixelSortSpan)
var compositePipeline = try compute.makePipeline(function: library.composite)
var params = Params(
width: UInt32(width),
height: UInt32(height),
sortKey: UInt32(key.metalValue),
lowerThreshold: lower,
upperThreshold: upper,
reverseSorting: descending ? 1 : 0,
gamma: gamma,
maxSpanLength: UInt32(maxSpan ?? width),
invertMask: invertMask ? 1 : 0
)
let paramBuffer = device.makeBuffer(
bytes: ¶ms, length: MemoryLayout<Params>.stride, options: .storageModeShared)!
// Mask
createMaskPipeline.arguments.colorTex = .texture(texA)
createMaskPipeline.arguments.maskTex = .texture(maskTex)
createMaskPipeline.arguments.params = .buffer(paramBuffer)
try compute.run(pipeline: createMaskPipeline, width: width, height: height)
// Clear span buffer
clearSpanPipeline.arguments.spanTex = .texture(spanTex)
clearSpanPipeline.arguments.params = .buffer(paramBuffer)
try compute.run(pipeline: clearSpanPipeline, width: width, height: height)
// Identify spans (1 thread per row: dispatch width=1)
identifySpansPipeline.arguments.maskTex = .texture(maskTex)
identifySpansPipeline.arguments.spanTex = .texture(spanTex)
identifySpansPipeline.arguments.params = .buffer(paramBuffer)
try compute.run(pipeline: identifySpansPipeline, width: 1, height: height)
// Sort each span into sortedTex
pixelSortPipeline.arguments.colorTex = .texture(texA)
pixelSortPipeline.arguments.spanTex = .texture(spanTex)
pixelSortPipeline.arguments.sortedTex = .texture(sortedTex)
pixelSortPipeline.arguments.params = .buffer(paramBuffer)
try compute.run(pipeline: pixelSortPipeline, width: 1, height: height)
// Composite only masked pixels into output texB
compositePipeline.arguments.maskTex = .texture(maskTex)
compositePipeline.arguments.sortedTex = .texture(sortedTex)
compositePipeline.arguments.originalTex = .texture(texA)
compositePipeline.arguments.outTex = .texture(texB)
compositePipeline.arguments.params = .buffer(paramBuffer)
try compute.run(pipeline: compositePipeline, width: width, height: height)
var outputData = [UInt8](repeating: 0, count: width * height * bytesPerPixel)
texB.getBytes(
&outputData,
bytesPerRow: bytesPerRow,
from: MTLRegionMake2D(0, 0, width, height),
mipmapLevel: 0
)
guard
let outCtx = CGContext(
data: &outputData,
width: width,
height: height,
bitsPerComponent: 8,
bytesPerRow: bytesPerRow,
space: colorSpace,
bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue
),
let outCGImage = outCtx.makeImage()
else {
throw ValidationError("Failed to create output image")
}
let nsOutImage = NSBitmapImageRep(cgImage: outCGImage)
let ext = outputURL.pathExtension.lowercased()
let fileType: NSBitmapImageRep.FileType = ext == "jpg" || ext == "jpeg" ? .jpeg : .png
guard let data = nsOutImage.representation(using: fileType, properties: [:]) else {
throw ValidationError("Failed to encode output image")
}
try data.write(to: outputURL)
print("Pixel-sorted image saved to \(self.output) (\(width)×\(height))")
}
}
struct Params {
var width: UInt32
var height: UInt32
var sortKey: UInt32
var lowerThreshold: Float
var upperThreshold: Float
var reverseSorting: UInt32
var gamma: Float
var maxSpanLength: UInt32
var invertMask: UInt32
}
enum SortKeyOption: String, ExpressibleByArgument, CaseIterable {
case brightness, hue, saturation, red, green, blue
var metalValue: Int {
switch self {
case .brightness: return 0
case .hue: return 1
case .saturation: return 2
case .red: return 3
case .green: return 4
case .blue: return 5
}
}
}
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