Add ImageAlignment sample using ORB and affine transform

test/OpenCvSharp.Tests/Img_alignment/ImageAlignmentTests.cs

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+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Drawing.Imaging;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OpenCvSharp.Tests.Img_alignment;
+
+internal class ImageAlignmentTests
+{
+    private static Mat templateMatGray;
+
+    /// <summary>
+    /// 初始化模板，只需调用一次
+    /// </summary>
+    public static void InitTemplate(Bitmap templateBitmap)
+    {
+        templateMatGray = BitmapToMat(templateBitmap);
+        Cv2.CvtColor(templateMatGray, templateMatGray, ColorConversionCodes.BGR2GRAY);
+    }
+
+    /// <summary>
+    /// 每帧对齐到模板
+    /// </summary>
+    public static Bitmap AlignToTemplate(Bitmap srcBitmap)
+    {
+        if (srcBitmap == null || templateMatGray == null)
+            return srcBitmap;
+
+        Mat srcMat = BitmapToMat(srcBitmap);
+        Mat srcGray = new Mat();
+        Cv2.CvtColor(srcMat, srcGray, ColorConversionCodes.BGR2GRAY);
+
+        // ORB 特征检测
+        var orb = ORB.Create(500);
+        KeyPoint[] kpTemplate, kpSrc;
+        Mat desTemplate = new Mat();
+        Mat desSrc = new Mat();
+        orb.DetectAndCompute(templateMatGray, null, out kpTemplate, desTemplate);
+        orb.DetectAndCompute(srcGray, null, out kpSrc, desSrc);
+
+        // BFMatcher 特征匹配
+        var bf = new BFMatcher(NormTypes.Hamming, crossCheck: true);
+        var matches = bf.Match(desTemplate, desSrc);
+        if (matches.Length < 4)
+            return srcBitmap; // 匹配点太少，直接返回原图
+
+        Array.Sort(matches, (a, b) => a.Distance.CompareTo(b.Distance));
+
+        var ptsTemplate = new Point2f[matches.Length];
+        var ptsSrc = new Point2f[matches.Length];
+        for (int i = 0; i < matches.Length; i++)
+        {
+            ptsTemplate[i] = kpTemplate[matches[i].QueryIdx].Pt;
+            ptsSrc[i] = kpSrc[matches[i].TrainIdx].Pt;
+        }
+
+        // 仿射矩阵
+        Mat mask = new Mat();
+        Mat M = Cv2.EstimateAffinePartial2D(InputArray.Create(ptsSrc), InputArray.Create(ptsTemplate), mask);
+        if (M.Empty())
+            return srcBitmap;
+
+        Mat aligned = new Mat();
+        Cv2.WarpAffine(srcMat, aligned, M, new Size(templateMatGray.Width, templateMatGray.Height));
+
+        return MatToBitmap(aligned);
+    }
+
+    #region Bitmap <-> Mat (无需 Extensions)
+
+    public static Mat BitmapToMat(Bitmap bitmap)
+    {
+        using (var ms = new System.IO.MemoryStream())
+        {
+            bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
+            byte[] bytes = ms.ToArray();
+            return Cv2.ImDecode(bytes, ImreadModes.Color); // 彩色
+        }
+    }
+
+    public static Bitmap MatToBitmap(Mat mat)
+    {
+        if (mat == null || mat.Empty())
+            return null;
+
+        Bitmap bmp;
+
+        if (mat.Channels() == 1)
+        {
+            // 灰度图
+            bmp = new Bitmap(mat.Width, mat.Height, PixelFormat.Format8bppIndexed);
+            BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height),
+                ImageLockMode.WriteOnly, bmp.PixelFormat);
+
+            // 创建缓冲区
+            int length = mat.Width * mat.Height;
+            byte[] buffer = new byte[length];
+            Marshal.Copy(mat.Data, buffer, 0, length);
+
+            // 拷贝到 Bitmap
+            Marshal.Copy(buffer, 0, data.Scan0, length);
+            bmp.UnlockBits(data);
+
+            // 设置灰度调色板
+            ColorPalette palette = bmp.Palette;
+            for (int i = 0; i < 256; i++)
+                palette.Entries[i] = Color.FromArgb(i, i, i);
+            bmp.Palette = palette;
+        }
+        else if (mat.Channels() == 3)
+        {
+            // 彩色图 BGR -> RGB
+            Mat rgbMat = new Mat();
+            Cv2.CvtColor(mat, rgbMat, ColorConversionCodes.BGR2RGB);
+
+            bmp = new Bitmap(rgbMat.Width, rgbMat.Height, PixelFormat.Format24bppRgb);
+            BitmapData data = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height),
+                ImageLockMode.WriteOnly, bmp.PixelFormat);
+
+            int length = rgbMat.Rows * int.Parse(rgbMat.Step().ToString());
+            byte[] buffer = new byte[length];
+            Marshal.Copy(rgbMat.Data, buffer, 0, length);
+            Marshal.Copy(buffer, 0, data.Scan0, length);
+
+            bmp.UnlockBits(data);
+        }
+        else
+        {
+            throw new NotSupportedException("Unsupported Mat format: channels=" + mat.Channels());
+        }
+
+        return new Bitmap(bmp); // 返回安全副本
+    }
+
+    #endregion
+}
+

test/OpenCvSharp.Tests/Img_alignment/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace OpenCvSharp.Tests.Img_alignment;
+
+internal class Program
+{
+    static void Main()
+    {
+        Console.WriteLine("=== Image Alignment Demo ===");
+
+        // 初始化模板
+        Bitmap template = new Bitmap("template.jpg");
+        ImageAlignmentTests.InitTemplate(template);
+
+        // 模拟每帧输入（摄像头帧）
+        Bitmap frame = new Bitmap("input.jpg");
+
+        Bitmap aligned = ImageAlignmentTests.AlignToTemplate(frame);
+
+        aligned.Save("aligned_output.jpg");
+        Console.WriteLine("Aligned image saved!");
+    }
+}