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OcrFinalHelper.cs

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+using System;
+using System.IO;
+using System.Drawing;
+using System.Drawing.Imaging;
+using Tesseract;
+
+public static class OcrFinalHelper
+{
+    private static readonly string _tessDataPath =
+        Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "tessdata");
+
+    /// <summary>
+    /// 针对白底黑字/截图优化的中文识别（强化浅灰色文字处理）
+    /// </summary>
+    public static string RecognizeScreenshot(string imagePath)
+    {
+        if (!File.Exists(imagePath))
+            return "文件不存在";
+
+        try
+        {
+            using var original = new Bitmap(imagePath);
+            using var scaled = ScaleImage(original, original.Width * 2, original.Height * 2);
+
+            // 预处理：灰度 → 对比度拉伸 → OTSU 二值化
+            using var gray = ToGrayscale(scaled);
+            using var stretched = AutoContrast(gray);
+            using var binary = BinarizeOtsu(stretched);
+
+            using var engine = new TesseractEngine(
+                _tessDataPath,
+                "chi_sim+eng",
+                EngineMode.LstmOnly);
+
+            engine.SetVariable("preserve_interword_spaces", "1");
+            engine.SetVariable("tessedit_pageseg_mode", "6");
+            engine.SetVariable("textord_min_linesize", "2.5");
+
+            using var pix = BitmapToPix(binary);
+            using var result = engine.Process(pix);
+
+            return result.GetText()?.Trim() ?? "";
+        }
+        catch (Exception ex)
+        {
+            return $"识别失败：{ex.Message}";
+        }
+    }
+
+    #region 预处理
+
+    private static Bitmap ScaleImage(Bitmap original, int newWidth, int newHeight)
+    {
+        var scaled = new Bitmap(newWidth, newHeight);
+        using (var g = Graphics.FromImage(scaled))
+        {
+            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
+            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
+            g.DrawImage(original, 0, 0, newWidth, newHeight);
+        }
+        return scaled;
+    }
+
+    private static Bitmap ToGrayscale(Bitmap bmp)
+    {
+        var gray = new Bitmap(bmp.Width, bmp.Height);
+        using (var g = Graphics.FromImage(gray))
+        {
+            var cm = new ColorMatrix(new float[][]
+            {
+                new float[]{0.299f,0.299f,0.299f,0,0},
+                new float[]{0.587f,0.587f,0.587f,0,0},
+                new float[]{0.114f,0.114f,0.114f,0,0},
+                new float[]{0,0,0,1,0},
+                new float[]{0,0,0,0,1}
+            });
+            using (var ia = new ImageAttributes())
+            {
+                ia.SetColorMatrix(cm);
+                g.DrawImage(bmp, new Rectangle(0, 0, bmp.Width, bmp.Height),
+                    0, 0, bmp.Width, bmp.Height, GraphicsUnit.Pixel, ia);
+            }
+        }
+        return gray;
+    }
+    
+    /// <summary>
+    /// 强化版对比度拉伸（专门优化：浅灰文字 + 低对比度文字）
+    /// 不破坏图像、不炸图、Tesseract 可正常识别
+    /// </summary>
+    private static Bitmap AutoContrast(Bitmap gray)
+    {
+        int min = 255, max = 0;
+        int width = gray.Width;
+        int height = gray.Height;
+
+        // 第一步：统计灰度（忽略纯白 255，避免背景干扰文字）
+        for (int y = 0; y < height; y++)
+        {
+            for (int x = 0; x < width; x++)
+            {
+                int val = gray.GetPixel(x, y).R;
+                if (val == 255) continue; // 跳过纯白背景
+                if (val < min) min = val;
+                if (val > max) max = val;
+            }
+        }
+
+        // 如果无有效内容，返回原图
+        if (min >= max || max - min < 10)
+            return (Bitmap)gray.Clone();
+
+        // 第二步：强化拉伸（专门强化 180~240 浅灰色文字）
+        Bitmap result = new Bitmap(width, height);
+        for (int y = 0; y < height; y++)
+        {
+            for (int x = 0; x < width; x++)
+            {
+                int val = gray.GetPixel(x, y).R;
+
+                // 核心：浅灰色文字强制增强
+                if (val >= 180 && val <= 245)
+                {
+                    val = val - 30; // 把浅灰 → 变深灰
+                }
+
+                // 标准对比度拉伸（强化文字边缘）
+                int newVal = (int)(((val - min) / (double)(max - min)) * 220 + 20);
+                newVal = Math.Clamp(newVal, 0, 255);
+
+                result.SetPixel(x, y, Color.FromArgb(newVal, newVal, newVal));
+            }
+        }
+
+        return result;
+    }
+    /// <summary>
+    /// OTSU 大津法二值化，自动寻找最佳阈值，适应各种灰度文字
+    /// </summary>
+    private static Bitmap BinarizeOtsu(Bitmap gray)
+    {
+        int[] histogram = new int[256];
+        int totalPixels = gray.Width * gray.Height;
+
+        // 统计直方图
+        for (int y = 0; y < gray.Height; y++)
+        {
+            for (int x = 0; x < gray.Width; x++)
+            {
+                int val = gray.GetPixel(x, y).R;
+                histogram[val]++;
+            }
+        }
+
+        // 计算 OTSU 阈值
+        double sum = 0;
+        for (int i = 0; i < 256; i++)
+            sum += i * histogram[i];
+
+        double sumB = 0;
+        int wB = 0, wF = 0;
+        double maxVariance = 0;
+        int threshold = 128; // 默认
+
+        for (int t = 0; t < 256; t++)
+        {
+            wB += histogram[t];               // 背景像素数
+            if (wB == 0) continue;
+            wF = totalPixels - wB;            // 前景像素数
+            if (wF == 0) break;
+
+            sumB += t * histogram[t];
+            double mB = sumB / wB;            // 背景平均灰度
+            double mF = (sum - sumB) / wF;    // 前景平均灰度
+
+            double variance = wB * (double)wF * (mB - mF) * (mB - mF);
+            if (variance > maxVariance)
+            {
+                maxVariance = variance;
+                threshold = t;
+            }
+        }
+
+        // 白底黑字：大于阈值 -> 白，否则 -> 黑
+        var bin = new Bitmap(gray.Width, gray.Height);
+        for (int y = 0; y < gray.Height; y++)
+        {
+            for (int x = 0; x < gray.Width; x++)
+            {
+                int val = gray.GetPixel(x, y).R;
+                bin.SetPixel(x, y, val > threshold ? Color.White : Color.Black);
+            }
+        }
+        return bin;
+    }
+
+    private static Pix BitmapToPix(Bitmap bmp)
+    {
+        using var ms = new MemoryStream();
+        bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
+        ms.Position = 0;
+        return Pix.LoadFromMemory(ms.ToArray());
+    }
+
+    #endregion
+}