new file: assets/picture21.jpg

.gitignore

@@ -1,7 +1,12 @@
 /qrCamera/bin
 /qrCamera/obj
 /qrCamera/cache
+/qrCameraAI/bin
+/qrCameraAI/obj
+/qrCameraAI/cache
 /createqrcodes/bin
 /createqrcodes/obj
+/cache
 /qr
 /createqr
+/qrcam

Makefile

@@ -5,9 +5,18 @@ qr:
 clean:
 	rm -rf qrCamera/bin/
 	rm -rf qrCamera/obj/
+	rm -rf qrCamera/cache/
+	rm -rf cache/
 	rm -rf createqrcodes/obj/
 	rm -rf createqrcodes/bin/
 	rm -f createqr
+	rm -f qrcam
 	rm -rf qr/
 run:
 	dotnet run -p:qrCamera/CameraPreview.csproj
+runai:
+	dotnet run -p:qrCameraAI/CameraPreview.csproj
+publish:
+	dotnet publish qrCamera/CameraPreview.csproj --self-contained true
+publishai:
+	dotnet publish qrCameraAI/CameraPreview.csproj --self-contained true

qrCamera/Program.cs

@@ -7,6 +7,9 @@ using ZXing.Common;
 using System.Runtime.InteropServices;
 using System.Drawing;
 using System.Net;
+using System.Runtime.InteropServices.Marshalling;
+using Emgu.CV.Face;
+using System.Transactions;
 
 // using Emgu.CV.CvEnum;
 
@@ -15,6 +18,7 @@ namespace BarcodeReaderExample
 {
     class Program
     {
+        static bool draw;
         static void Main(string[] args)
         {
             VideoCapture camera = new VideoCapture("/dev/video0", VideoCaptureAPIs.V4L2);
@@ -24,16 +28,21 @@ namespace BarcodeReaderExample
 
             camera.Set(VideoCaptureProperties.FrameWidth, 1280);
             camera.Set(VideoCaptureProperties.FrameHeight, 720);
-            camera.Set(VideoCaptureProperties.Fps, 24);
+            int fps = 60;
-            if(Directory.Exists("cache"))
+            int avalibeImages = 20;
+            camera.Set(VideoCaptureProperties.Fps, fps);
+            if (Directory.Exists("cache"))
             {
-                Directory.Delete("cache",true);
+                Directory.Delete("cache", true);
             }
 
             Directory.CreateDirectory("cache");
             Mat hey = new Mat("photo.png");
-            Mat[] Cached = new Mat[10];
+            Mat[] Cached = new Mat[avalibeImages];
+            draw = true;
 
+            int imgX = 0;
+            int imgY = 0;
 
             using var rgb = new Mat();
 
@@ -44,35 +53,40 @@ namespace BarcodeReaderExample
 
 
             Cv2.NamedWindow("Camera preview", WindowFlags.AutoSize);
-            int photocount = 0;
+            // Mat src = Cv2.ImRead("test.png");
-                    Mat src = Cv2.ImRead("test.png");
+            int whenWasLastTimeQrDetected = 0;
-
+            Mat Lastimage = new Mat();
-
+            IEnumerable<IEnumerable<OpenCvSharp.Point>> contours = null;
-
+                    // PointF[] location;
-            string[] files = new string[10];
+            Mat previue = new Mat();
-            int files_index =0;
+            string[] files = new string[avalibeImages];
+            int files_index = 0;
             while (true)
             {
-                // if (!camera.Read(frame) || frame.Empty())
+
-                // {
+
-                //     Console.Error.WriteLine("Nie udało się odczytać klatki");
-                //     break;
-                // }
                 camera.Read(frame);
 
+                Result result = ReadQrCode(frame);
+// Console.WriteLine(Lastimage.Empty());
+                if (!(Lastimage.Empty()))
+                {
+                    Cv2.Resize(Lastimage, previue, new OpenCvSharp.Size(500, 500));
+
+                    Mat roi2 = frame[new Rect(0, 0, previue.Width, previue.Height)];
+                    previue.CopyTo(roi2);
+                }
 
-                Result result = GetResult(frame);
                 if (result != null)
                 {
+                    whenWasLastTimeQrDetected = 5;
                     List<ResultPoint> points = result.ResultPoints.ToList();
                     float[] pos1 = new float[2] { points[0].X, points[0].Y }; /// lewy dolny róg
                     float[] pos2 = new float[2] { points[2].X, points[2].Y };   ///prawy górny róg
                     float[] pos3 = new float[2] { points[1].X, points[1].Y };   ///lewy górny róg
                     int width = (int)(pos2[0] - pos3[0]);
                     int heigh = (int)(pos1[1] - pos3[1]);
-                    // Cv2.Circle(frame, (int)pos1[0], (int)pos1[1], 5, Scalar.Red, 2);
+
-                    // Cv2.Circle(frame, (int)pos2[0], (int)pos2[1], 5, Scalar.Green, 2);
-                    // Cv2.Circle(frame, (int)pos3[0], (int)pos3[1], 5, Scalar.Blue, 2);  
                     PointF[] location;
                     try
                     {
@@ -83,19 +97,6 @@ namespace BarcodeReaderExample
                     {
                         continue;
                     }
-
-
-                    // Mat roi = frame[new Rect((int)pos3[0],(int)pos3[1], src.Width+3, src.Height)];
-                    Mat roi = frame[new Rect((int)pos3[0], (int)pos3[1], width,heigh)];
-                    src.CopyTo(roi);
-                    // Console.WriteLine($"szerokość:{width}");
-                    // Console.WriteLine($"wysokosc:{heigh}");
-                    // Console.WriteLine($"x:{pos3[0]}");
-                    // Console.WriteLine($"y:{pos3[1]}");
-
-                    // DrawLine(location);    //draw red squre
-
-
                     var points1 = new List<OpenCvSharp.Point>
 {
     GetPoint(location[0]),
@@ -103,23 +104,28 @@ namespace BarcodeReaderExample
     GetPoint(location[3]),
     GetPoint(location[2])
 };
-
+                    int qrWidth = GetPoint(location[1]).X - GetPoint(location[0]).X;
-                    // Zagnieźdź w dodatkową kolekcję:
+                    int qrHeigh = GetPoint(location[2]).Y - GetPoint(location[0]).Y;
-                    IEnumerable<IEnumerable<OpenCvSharp.Point>> contours = new[] { points1 };
 
 
-                    // Cv2.FillPoly(frame, contours, Scalar.White);   // fill with white
+                    imgX = GetPoint(location[0]).X;
+                    imgY = GetPoint(location[0]).Y;
+                    contours = new[] { points1 };
 
-                    Cv2.PutText(frame, result.Text, new OpenCvSharp.Point((int)(pos2[0]-pos3[0])/2+(int)pos3[0]-160, (int)(pos2[1]-pos3[1])/2+(int)pos3[1]+60), HersheyFonts.HersheySimplex, 0.8, Scalar.Black, 2);
+                    if (draw)
+                        Cv2.FillPoly(frame, contours, Scalar.White);   // fill with white
+
+                    //Write Text
+                    // Cv2.PutText(frame, result.Text, new OpenCvSharp.Point((int)(pos2[0]-pos3[0])/2+(int)pos3[0]-160, (int)(pos2[1]-pos3[1])/2+(int)pos3[1]+60), HersheyFonts.HersheySimplex, 0.8, Scalar.Black, 2);
 
                     if (!files.Contains(result.Text))
                     {
                         files[files_index] = result.Text;
-                    Console.WriteLine("downloading: "+result.Text);
+                        Console.WriteLine("downloading: " + result.Text);
 
                         using (var client = new WebClient())
                         {
-                            client.DownloadFile(result.Text, "cache/"+files_index + ".png");
+                            client.DownloadFile(result.Text, "cache/" + files_index + ".png");
                             // Thread.Sleep(2000);
 
                         }
@@ -128,37 +134,59 @@ namespace BarcodeReaderExample
                     }
                     else
                     {
-                        // try
-                        // {
 
                         int toload = files.IndexOf(result.Text);
+                        Mat toDraw= new Mat();
+
+
+                        InputArray inputArray = toDraw;
+                        // Console.WriteLine($"{qrWidth} , {qrHeigh}");
+
+                        try
+                        {
+                            
+                        Cv2.Resize(Cached[toload],toDraw,new OpenCvSharp.Size(qrWidth,qrHeigh));
+                        }
+                        catch
+                        { continue; }
+                        Lastimage = toDraw;
+
+                        // toDraw.Resize(1,3);
+                        try
+                        {
+
+                            // Mat roi2 = frame[new Rect(GetPoint(location[0]).X, GetPoint(location[0]).Y, toDraw.Width, toDraw.Height)];
+                            // toDraw.CopyTo(roi2);
+                            DrawImage(toDraw, GetPoint(location[0]).X, GetPoint(location[0]).Y);
+
+                        }
+                        catch { }
 
-                            Mat roi2 = frame[new Rect((int)pos3[0], (int)pos3[1], Cached[toload].Width, Cached[toload].Height)];
-                            Cached[toload].CopyTo(roi2);
-                            // Console.WriteLine("work");
-                        // }
-                        // catch { }
                     }
 
 
-                    // Cv2.draw
-
-                    // Cv2.Circle(frame, (int)(RightBottomX), (int)(RightBottomY), 5, Scalar.Green, 2);  
-
-                    //Cv2.Rectangle(frame, new Point((int)X, (int)Y), new Point ((int)Width, (int)Height), Scalar.Red, 2); 
-                    // Console.WriteLine(result.Text);
                 }
+                else if (whenWasLastTimeQrDetected > 0)
+                {
+                    if (draw)
+                        Cv2.FillPoly(frame, contours, Scalar.White);   // fill with white
 
+                    try
+                    {
+                        // Mat roi2 = frame[new Rect(imgX, imgY, Lastimage.Width, Lastimage.Height)];
+                        // Lastimage.CopyTo(roi2);
 
+                        DrawImage(Lastimage,imgX,imgY);
+                    }
+                    catch { }
+                    whenWasLastTimeQrDetected--;
 
-
+                }
-                // frame.SaveImage($"photos/photo_{photocount}.png");
-                // photocount++;
 
 
                 Cv2.ImShow("Camera preview", frame);
-                Thread.Sleep(1000 / 24);
+                Thread.Sleep(1000 / fps);
-                // Console.WriteLine("tick");
+
                 int key = Cv2.WaitKey(1);
                 if (key == 27 || key == 'q')
                     break;
@@ -167,9 +195,19 @@ namespace BarcodeReaderExample
             Cv2.DestroyAllWindows();
 
         }
+
+        static void DrawImage(Mat image, int posX, int posY)
+        {
+            if(draw)
+            {
+                
+            Mat roi2 = frame[new Rect(posX, posY, image.Width, image.Height)];
+            image.CopyTo(roi2);
+            }
+        }
         static OpenCvSharp.Point GetPoint(PointF pointf)
         {
-            return new OpenCvSharp.Point(pointf.X,pointf.Y);
+            return new OpenCvSharp.Point(pointf.X, pointf.Y);
         }
         static PointF[] Calculate(float[] pos1, float[] pos2, float[] pos3, float[] pos4)
         {
@@ -207,7 +245,7 @@ namespace BarcodeReaderExample
             PointF topRight = Expand(p2);
             PointF bottomRight = ExpandLB(p4);
             PointF bottomLeft = Expand(p1);
-            PointF[] Location = new PointF[] {topLeft,topRight,bottomLeft,bottomRight};
+            PointF[] Location = new PointF[] { topLeft, topRight, bottomLeft, bottomRight };
             return Location;
             // 4. Now draw the 4 lines
             // Example with System.Drawing or Unity or whatever you use:
@@ -215,7 +253,11 @@ namespace BarcodeReaderExample
         }
         static void DrawLine(PointF p1, PointF p2)
         {
+            if(draw)
+            {
+                
             Cv2.Line(frame, (int)p1.X, (int)p1.Y, (int)p2.X, (int)p2.Y, Scalar.Red, 2);
+            }
 
         }
         static void DrawLine(PointF[] Location)
@@ -234,7 +276,7 @@ namespace BarcodeReaderExample
         }
         static Mat frame = new Mat();
 
-        static Result GetResult(Mat frame)
+        static Result ReadQrCode(Mat frame)
         {
 
             QRCodeReader reader = new QRCodeReader();
@@ -288,13 +330,3 @@ namespace BarcodeReaderExample
     }
 }
 
-
-
-
-
-
-
-
-
-
-

qrCameraAI/CameraPreview.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Emgu.CV" Version="4.13.0.5924" />
+    <PackageReference Include="Emgu.CV.Bitmap" Version="4.13.0.5924" />
+    <PackageReference Include="OpenCvSharp4" Version="4.13.0.20260627" />
+    <PackageReference Include="OpenCvSharp4.Extensions" Version="4.13.0.20260627" />
+    <PackageReference Include="OpenCvSharp4.official.runtime.linux-x64" Version="4.13.0.20260627" />
+    <PackageReference Include="ZXing.Net" Version="0.16.11" />
+    <PackageReference Include="ZXing.Net.Bindings.Windows.Compatibility" Version="0.16.14" />
+  </ItemGroup>
+
+</Project>

qrCameraAI/Program.cs

@@ -0,0 +1,384 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Net.Http;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using OpenCvSharp;
+using ZXing;
+using ZXing.Common;
+using ZXing.Multi;
+using ZXing.QrCode;
+
+namespace BarcodeReaderExample
+{
+    class Program
+    {
+        // ---- tunables -------------------------------------------------
+        const bool EnableOverlay = true;          // master draw switch (debug)
+        const bool TryHarderMultiDecode = true;    // more reliable multi-QR detection, costs some speed
+        const float QuadExpansion = 1.50f;         // how much bigger than the QR the overlay is drawn
+        const int MaxMissedFrames = 8;             // keep last known position this many frames if briefly lost
+        const int TargetFps = 24;
+        const float LocalRedetectPadding = 0.6f;   // extra search margin around last known box, as a fraction of its size
+        const int LocalRedetectUpscale = 3;        // how much to enlarge the crop before decoding it
+
+        static readonly HttpClient Http = new HttpClient();
+        static readonly ConcurrentDictionary<string, Mat> ImageCache = new();   // text -> decoded image (null = failed)
+        static readonly ConcurrentDictionary<string, byte> Pending = new();     // text currently downloading
+
+        static readonly QRCodeReader QrReader = new QRCodeReader();
+        static readonly GenericMultipleBarcodeReader MultiReader = new GenericMultipleBarcodeReader(QrReader);
+        static readonly Dictionary<DecodeHintType, object> Hints = new()
+        {
+            { DecodeHintType.POSSIBLE_FORMATS, new List<BarcodeFormat> { BarcodeFormat.QR_CODE } },
+            { DecodeHintType.TRY_HARDER, TryHarderMultiDecode },
+        };
+        // Used only for the small, targeted local-redetect crop, so the extra cost is negligible there.
+        static readonly Dictionary<DecodeHintType, object> LocalHints = new()
+        {
+            { DecodeHintType.POSSIBLE_FORMATS, new List<BarcodeFormat> { BarcodeFormat.QR_CODE } },
+            { DecodeHintType.TRY_HARDER, true },
+            { DecodeHintType.ALSO_INVERTED, true },
+        };
+
+        static readonly CLAHE Clahe = Cv2.CreateCLAHE(clipLimit: 3.0, tileGridSize: new Size(8, 8));
+
+        static byte[] _grayBuffer;
+        static readonly Dictionary<string, TrackedQr> Tracked = new();
+
+        class TrackedQr
+        {
+            public Point2f[] RawQuad;    // TL, TR, BR, BL as detected, unexpanded - used to seed the next search
+            public Point2f[] Quad;       // TL, TR, BR, BL, expanded - used for drawing
+            public int MissedFrames;
+        }
+
+        static void Main(string[] args)
+        {
+            using VideoCapture camera = new VideoCapture("/dev/video0", VideoCaptureAPIs.V4L2);
+            if (!camera.IsOpened())
+                throw new Exception("Nie można otworzyć kamery /dev/video0");
+
+            camera.Set(VideoCaptureProperties.FrameWidth, 1280);
+            camera.Set(VideoCaptureProperties.FrameHeight, 720);
+            camera.Set(VideoCaptureProperties.Fps, TargetFps);
+
+            Cv2.NamedWindow("Camera preview", WindowFlags.AutoSize);
+
+            using var frame = new Mat();
+            using var gray = new Mat();
+            var sw = Stopwatch.StartNew();
+            var frameTimer = Stopwatch.StartNew();
+            int frameCount = 0;
+            double fps = 0;
+
+            try
+            {
+                while (true)
+                {
+                    frameTimer.Restart();
+
+                    if (!camera.Read(frame) || frame.Empty())
+                        continue;
+
+                    try
+                    {
+                        ProcessFrame(frame, gray);
+                    }
+                    catch (Exception ex)
+                    {
+                        // Never let a single bad frame kill the capture loop.
+                        Console.WriteLine("Frame processing error: " + ex.Message);
+                    }
+
+                    frameCount++;
+                    if (sw.ElapsedMilliseconds >= 500)
+                    {
+                        fps = frameCount / (sw.ElapsedMilliseconds / 1000.0);
+                        frameCount = 0;
+                        sw.Restart();
+                    }
+                    Cv2.PutText(frame, $"{fps:0.0} fps", new Point(10, frame.Height - 15),
+                        HersheyFonts.HersheySimplex, 0.6, Scalar.Lime, 2);
+
+                    Cv2.ImShow("Camera preview", frame);
+
+                    // Only sleep for whatever time is left in the frame budget instead of
+                    // always sleeping the full 1000/fps on top of WaitKey (which halved
+                    // the effective frame rate in the original code).
+                    int budgetMs = 1000 / TargetFps;
+                    int elapsedMs = (int)frameTimer.ElapsedMilliseconds;
+                    int waitMs = Math.Max(1, budgetMs - elapsedMs);
+
+                    int key = Cv2.WaitKey(waitMs);
+                    if (key == 27 || key == 'q')
+                        break;
+                }
+            }
+            finally
+            {
+                foreach (var mat in ImageCache.Values)
+                    mat?.Dispose();
+                Cv2.DestroyAllWindows();
+            }
+        }
+
+        static void ProcessFrame(Mat frame, Mat gray)
+        {
+            Cv2.CvtColor(frame, gray, ColorConversionCodes.BGR2GRAY);
+
+            // Contrast-normalize before decoding - this is the single biggest lever for detection
+            // reliability under uneven lighting (glare, shadow across part of the code, dim rooms).
+            using var enhanced = new Mat();
+            Clahe.Apply(gray, enhanced);
+
+            Result[] results = ReadQrCodes(enhanced);
+
+            var seenThisFrame = new HashSet<string>();
+
+            foreach (var result in results)
+            {
+                if (result?.Text == null) continue;
+                var (pTL, pTR, pBR, pBL) = CornersFromResult(result);
+                if (pTL == null) continue;
+
+                UpdateTracked(result.Text, pTL.Value, pTR.Value, pBR.Value, pBL.Value);
+                seenThisFrame.Add(result.Text);
+                EnsureImageLoaded(result.Text);
+            }
+
+            // For codes we're already tracking but the global pass didn't find this frame, actively
+            // re-search a small, upscaled crop around their last known position instead of just
+            // freezing them in place. This recovers far more often for codes that are small,
+            // partially blurred, or at a steep angle - the global full-frame pass is much less
+            // likely to catch those, but a zoomed-in targeted decode often still can.
+            foreach (var kv in Tracked)
+            {
+                if (seenThisFrame.Contains(kv.Key)) continue;
+                if (TryLocalRedetect(enhanced, kv.Value.RawQuad, out var pTL, out var pTR, out var pBR, out var pBL))
+                {
+                    UpdateTracked(kv.Key, pTL, pTR, pBR, pBL);
+                    seenThisFrame.Add(kv.Key);
+                }
+            }
+
+            // Age out codes that weren't seen this frame; keep them briefly to avoid flicker.
+            List<string> toRemove = null;
+            foreach (var kv in Tracked)
+            {
+                if (seenThisFrame.Contains(kv.Key)) continue;
+                kv.Value.MissedFrames++;
+                if (kv.Value.MissedFrames > MaxMissedFrames)
+                    (toRemove ??= new List<string>()).Add(kv.Key);
+            }
+            if (toRemove != null)
+                foreach (var key in toRemove) Tracked.Remove(key);
+
+            if (!EnableOverlay) return;
+
+            foreach (var kv in Tracked)
+            {
+                if (ImageCache.TryGetValue(kv.Key, out Mat img) && img != null && !img.Empty())
+                {
+                    OverlayImagePerspective(frame, img, kv.Value.Quad);
+                }
+            }
+        }
+
+        static void UpdateTracked(string text, Point2f tl, Point2f tr, Point2f br, Point2f bl)
+        {
+            Point2f[] raw = { tl, tr, br, bl };
+            Point2f[] quad = ExpandQuad(tl, tr, br, bl, QuadExpansion);
+
+            if (Tracked.TryGetValue(text, out var t))
+            {
+                t.RawQuad = raw;
+                t.Quad = quad;
+                t.MissedFrames = 0;
+            }
+            else
+            {
+                Tracked[text] = new TrackedQr { RawQuad = raw, Quad = quad, MissedFrames = 0 };
+            }
+        }
+
+        /// <summary>
+        /// ZXing QR point order: [0]=bottom-left, [1]=top-left, [2]=top-right, optional [3]=alignment
+        /// pattern. We deliberately do NOT use points[3] for the bottom-right corner: the alignment
+        /// pattern sits several modules inset from the actual edge of the code, so it's always
+        /// noticeably closer to the center than the true corner is - using it directly shrinks that
+        /// whole side of the overlay. Instead derive the true bottom-right corner from the 3
+        /// finder-pattern corners, which ZXing locates precisely, assuming the QR is (near) square:
+        /// BR = TR + BL - TL.
+        /// </summary>
+        static (Point2f? tl, Point2f? tr, Point2f? br, Point2f? bl) CornersFromResult(Result result)
+        {
+            var points = result?.ResultPoints;
+            if (points == null || points.Length < 3) return (null, null, null, null);
+
+            Point2f pBL = new Point2f(points[0].X, points[0].Y);
+            Point2f pTL = new Point2f(points[1].X, points[1].Y);
+            Point2f pTR = new Point2f(points[2].X, points[2].Y);
+            Point2f pBR = new Point2f(pTR.X + pBL.X - pTL.X, pTR.Y + pBL.Y - pTL.Y);
+            return (pTL, pTR, pBR, pBL);
+        }
+
+        /// <summary>Expand a quad (TL,TR,BR,BL) outward from its centroid by a scale factor.</summary>
+        static Point2f[] ExpandQuad(Point2f tl, Point2f tr, Point2f br, Point2f bl, float scale)
+        {
+            float cx = (tl.X + tr.X + br.X + bl.X) / 4f;
+            float cy = (tl.Y + tr.Y + br.Y + bl.Y) / 4f;
+
+            Point2f Expand(Point2f p) => new Point2f(cx + (p.X - cx) * scale, cy + (p.Y - cy) * scale);
+
+            return new[] { Expand(tl), Expand(tr), Expand(br), Expand(bl) };
+        }
+
+        /// <summary>
+        /// Warp `overlayImage` onto the quadrilateral `quad` (TL,TR,BR,BL) in `frame`, so the
+        /// pasted image follows the QR code's rotation/perspective instead of a plain axis-aligned resize.
+        /// Only the quad's bounding box is warped, not the whole frame, to keep this fast with
+        /// several codes on screen at once.
+        /// </summary>
+        static void OverlayImagePerspective(Mat frame, Mat overlayImage, Point2f[] quad)
+        {
+            var intPoints = quad.Select(p => new Point((int)p.X, (int)p.Y)).ToArray();
+            Rect rect = Cv2.BoundingRect(intPoints);
+            rect = rect.Intersect(new Rect(0, 0, frame.Width, frame.Height));
+            if (rect.Width <= 1 || rect.Height <= 1) return;
+
+            int w = overlayImage.Width, h = overlayImage.Height;
+            Point2f[] src = { new(0, 0), new(w, 0), new(w, h), new(0, h) };
+            Point2f[] dstLocal = quad.Select(p => new Point2f(p.X - rect.X, p.Y - rect.Y)).ToArray();
+
+            using Mat homography = Cv2.GetPerspectiveTransform(src, dstLocal);
+            using var warped = new Mat();
+            Cv2.WarpPerspective(overlayImage, warped, homography, rect.Size);
+
+            using var mask = new Mat(rect.Size, MatType.CV_8UC1, Scalar.Black);
+            var localPoly = dstLocal.Select(p => new Point((int)p.X, (int)p.Y)).ToArray();
+            Cv2.FillPoly(mask, new[] { localPoly }, Scalar.White);
+
+            using var roi = new Mat(frame, rect);
+            warped.CopyTo(roi, mask);
+        }
+
+        // ---- decoding ---------------------------------------------------
+
+        static Result[] ReadQrCodes(Mat gray)
+        {
+            var luminanceSource = ToLuminanceSource(gray, ref _grayBuffer);
+            var bitmap = new BinaryBitmap(new HybridBinarizer(luminanceSource));
+
+            try
+            {
+                return MultiReader.decodeMultiple(bitmap, Hints) ?? Array.Empty<Result>();
+            }
+            catch
+            {
+                return Array.Empty<Result>();
+            }
+        }
+
+        /// <summary>
+        /// Crop tightly around a code's last known position (with padding for movement), upscale
+        /// that crop, and try to decode just it. Works much better than a full-frame scan for a
+        /// code that's already small, tilted, or motion-blurred, since the decoder effectively gets
+        /// a bigger, cleaner version of just the region that matters.
+        /// </summary>
+        static bool TryLocalRedetect(Mat enhanced, Point2f[] lastRaw, out Point2f tl, out Point2f tr, out Point2f br, out Point2f bl)
+        {
+            tl = tr = br = bl = default;
+            if (lastRaw == null) return false;
+
+            var intPoints = lastRaw.Select(p => new Point((int)p.X, (int)p.Y)).ToArray();
+            Rect box = Cv2.BoundingRect(intPoints);
+            int pad = (int)(Math.Max(box.Width, box.Height) * LocalRedetectPadding);
+            Rect search = new Rect(box.X - pad, box.Y - pad, box.Width + pad * 2, box.Height + pad * 2);
+            search = search.Intersect(new Rect(0, 0, enhanced.Width, enhanced.Height));
+            if (search.Width < 15 || search.Height < 15) return false;
+
+            using var crop = new Mat(enhanced, search);
+            using var scaled = new Mat();
+            Cv2.Resize(crop, scaled, new Size(crop.Width * LocalRedetectUpscale, crop.Height * LocalRedetectUpscale),
+                0, 0, InterpolationFlags.Cubic);
+
+            byte[] localBuffer = null;
+            var luminanceSource = ToLuminanceSource(scaled, ref localBuffer);
+            var bitmap = new BinaryBitmap(new HybridBinarizer(luminanceSource));
+
+            Result result;
+            try { result = QrReader.decode(bitmap, LocalHints); }
+            catch { return false; }
+            if (result == null) return false;
+
+            var (cTl, cTr, cBr, cBl) = CornersFromResult(result);
+            if (cTl == null) return false;
+
+            // Map corners from the upscaled crop back into full-frame coordinates.
+            Point2f ToFrame(Point2f p) => new Point2f(
+                search.X + p.X / LocalRedetectUpscale,
+                search.Y + p.Y / LocalRedetectUpscale);
+
+            tl = ToFrame(cTl.Value);
+            tr = ToFrame(cTr.Value);
+            br = ToFrame(cBr.Value);
+            bl = ToFrame(cBl.Value);
+            return true;
+        }
+
+        static RGBLuminanceSource ToLuminanceSource(Mat gray, ref byte[] buffer)
+        {
+            Mat continuous = gray.IsContinuous() ? gray : gray.Clone();
+            int size = (int)(continuous.Total() * continuous.ElemSize());
+            if (buffer == null || buffer.Length != size)
+                buffer = new byte[size];
+            Marshal.Copy(continuous.Data, buffer, 0, size);
+
+            // Gray8 skips ZXing's internal RGB->luminance conversion entirely - the fastest
+            // format to hand it, and matches what BGR2GRAY/CLAHE already produced for us.
+            var source = new RGBLuminanceSource(buffer, continuous.Width, continuous.Height, RGBLuminanceSource.BitmapFormat.Gray8);
+            if (!ReferenceEquals(continuous, gray))
+                continuous.Dispose();
+            return source;
+        }
+
+        // ---- async image download/caching --------------------------------
+
+        static void EnsureImageLoaded(string url)
+        {
+            if (ImageCache.ContainsKey(url) || Pending.ContainsKey(url)) return;
+
+            if (!Uri.TryCreate(url, UriKind.Absolute, out var uri) ||
+                (uri.Scheme != Uri.UriSchemeHttp && uri.Scheme != Uri.UriSchemeHttps))
+            {
+                // Not a downloadable URL - remember that so we don't keep retrying every frame.
+                ImageCache[url] = null;
+                return;
+            }
+
+            Pending[url] = 0;
+            _ = Task.Run(async () =>
+            {
+                try
+                {
+                    byte[] bytes = await Http.GetByteArrayAsync(uri);
+                    Mat decoded = Mat.FromImageData(bytes, ImreadModes.Color);
+                    ImageCache[url] = decoded.Empty() ? null : decoded;
+                }
+                catch (Exception ex)
+                {
+                    Console.WriteLine($"Failed to download {url}: {ex.Message}");
+                    ImageCache[url] = null; // negative-cache so we stop retrying a bad URL
+                }
+                finally
+                {
+                    Pending.TryRemove(url, out _);
+                }
+            });
+        }
+    }
+}