Split project into frontend and backend

backend/tools/vision_ocr.swift

@@ -0,0 +1,95 @@
+import AppKit
+import Foundation
+import Vision
+
+struct OCRLine {
+    let text: String
+    let x: CGFloat
+    let y: CGFloat
+}
+
+func pageNumber(from path: String) -> Int {
+    let name = URL(fileURLWithPath: path).deletingPathExtension().lastPathComponent
+    let digits = name.replacingOccurrences(of: "[^0-9]", with: "", options: .regularExpression)
+    return Int(digits) ?? 0
+}
+
+func loadCGImage(_ path: String) -> CGImage? {
+    let url = URL(fileURLWithPath: path)
+    guard let image = NSImage(contentsOf: url),
+          let tiff = image.tiffRepresentation,
+          let bitmap = NSBitmapImageRep(data: tiff) else {
+        return nil
+    }
+    return bitmap.cgImage
+}
+
+func recognize(_ path: String) throws -> [OCRLine] {
+    guard let cgImage = loadCGImage(path) else {
+        throw NSError(domain: "VisionOCR", code: 1, userInfo: [NSLocalizedDescriptionKey: "Could not load image: \(path)"])
+    }
+
+    var lines: [OCRLine] = []
+    var requestError: Error?
+    let request = VNRecognizeTextRequest { request, error in
+        if let error = error {
+            requestError = error
+            return
+        }
+        let observations = (request.results as? [VNRecognizedTextObservation]) ?? []
+        lines = observations.compactMap { observation in
+            guard let candidate = observation.topCandidates(1).first else { return nil }
+            let text = candidate.string.trimmingCharacters(in: .whitespacesAndNewlines)
+            guard !text.isEmpty else { return nil }
+            return OCRLine(text: text, x: observation.boundingBox.minX, y: observation.boundingBox.maxY)
+        }
+    }
+
+    request.recognitionLevel = .accurate
+    request.usesLanguageCorrection = true
+    request.recognitionLanguages = ["zh-Hans", "en-US"]
+
+    let handler = VNImageRequestHandler(cgImage: cgImage, options: [:])
+    try handler.perform([request])
+    if let requestError = requestError {
+        throw requestError
+    }
+
+    return lines.sorted {
+        if abs($0.y - $1.y) > 0.012 {
+            return $0.y > $1.y
+        }
+        return $0.x < $1.x
+    }
+}
+
+let args = Array(CommandLine.arguments.dropFirst())
+guard args.count >= 2 else {
+    FileHandle.standardError.write(Data("Usage: vision_ocr.swift OUTPUT.md IMAGE...\n".utf8))
+    exit(2)
+}
+
+let output = args[0]
+let imagePaths = args.dropFirst().sorted {
+    let lhs = pageNumber(from: $0)
+    let rhs = pageNumber(from: $1)
+    return lhs == rhs ? $0 < $1 : lhs < rhs
+}
+
+var result = "# GB/T 33923-2017 OCR 文本版\n\n"
+result += "> 说明：此文本由 PDF 页面图像 OCR 生成，用于阅读、搜索和复制。公式、表格、上下标和个别专业符号可能需要对照原 PDF 校核。\n\n"
+
+for (index, path) in imagePaths.enumerated() {
+    let page = pageNumber(from: path)
+    FileHandle.standardError.write(Data("OCR page \(index + 1)/\(imagePaths.count): \(URL(fileURLWithPath: path).lastPathComponent)\n".utf8))
+    do {
+        let lines = try recognize(path)
+        result += "\n\n## 第 \(page) 页\n\n"
+        result += lines.map(\.text).joined(separator: "\n")
+        result += "\n"
+    } catch {
+        result += "\n\n## 第 \(page) 页\n\n[OCR 失败：\(error.localizedDescription)]\n"
+    }
+}
+
+try result.write(toFile: output, atomically: true, encoding: .utf8)