Fix checked native barcode crop bounds

.github/workflows/_bot-build.yml

@@ -3,6 +3,10 @@ name: "Bot: Build"
 on:
   workflow_call:
     inputs:
+      runner:
+        type: string
+        default: ubuntu-22.04-arm
+        description: "Runner image for build and tests"
       test-command:
         required: true
         type: string
@@ -24,7 +28,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-22.04-arm
+    runs-on: ${{ inputs.runner }}
 
     steps:
     - uses: actions/checkout@v4

.github/workflows/_bot-deploy.yml

@@ -3,6 +3,10 @@ name: "Bot: Deploy"
 on:
   workflow_call:
     inputs:
+      runner:
+        type: string
+        default: ubuntu-22.04-arm
+        description: "Runner image for build and tests"
       test-command:
         required: true
         type: string
@@ -72,7 +76,7 @@ env:
 
 jobs:
   deploy:
-    runs-on: ubuntu-22.04-arm
+    runs-on: ${{ inputs.runner }}
     # VPN peer is single-occupancy per bot (PR #369 / my-infra#111 gave every
     # bot its own dedicated WireGuard peer — WIREGUARD_CONFIG_VAHTER/_COUPON/
     # _ALITA — so bots no longer share one peer). This group is scoped per

.github/workflows/coupon-build.yml

@@ -9,6 +9,7 @@ jobs:
   build:
     uses: ./.github/workflows/_bot-build.yml
     with:
+      runner: ubuntu-24.04-arm
       test-command: |
         dotnet test tests/CouponHubBot.Tests/CouponHubBot.Tests.fsproj -c Release --logger "trx;LogFileName=test-results.trx" --logger "console;verbosity=detailed"
         dotnet test tests/CouponHubBot.Ocr.Tests/CouponHubBot.Ocr.Tests.fsproj -c Release --logger "trx;LogFileName=test-results.trx" --logger "console;verbosity=detailed"

.github/workflows/coupon-deploy.yml

@@ -40,6 +40,7 @@ jobs:
   deploy:
     uses: ./.github/workflows/_bot-deploy.yml
     with:
+      runner: ubuntu-24.04-arm
       test-command: |
         dotnet test tests/CouponHubBot.Tests/CouponHubBot.Tests.fsproj -c Release --logger "trx;LogFileName=test-results.trx"
         dotnet test tests/CouponHubBot.Ocr.Tests/CouponHubBot.Ocr.Tests.fsproj -c Release --logger "trx;LogFileName=test-results.trx"

src/CouponHubBot/CouponHubBot.fsproj

@@ -7,6 +7,7 @@
     <Compile Include="Services/DbService.fs" />
     <Compile Include="Services/MembershipService.fs" />
     <Compile Include="Services/NotificationService.fs" />
+    <Compile Include="Services/CouponBarcodeReader.fs" />
     <Compile Include="Services/CouponOcrEngine.fs" />
     <Compile Include="Services/GitHubService.fs" />
     <Compile Include="Services/ReminderService.fs" />

src/CouponHubBot/Services/CouponBarcodeReader.fs

@@ -0,0 +1,61 @@
+namespace CouponHubBot.Services
+
+open System
+open System.IO
+open SixLabors.ImageSharp
+open SixLabors.ImageSharp.PixelFormats
+
+module CouponBarcodeReader =
+    let tryDecode (imageBytes: ReadOnlyMemory<byte>) =
+        // Resolve the library before constructing objects with native finalizers.
+        let format = ZXingCpp.BarcodeFormat.Parse("EAN13")
+        use ms = new MemoryStream(imageBytes.ToArray())
+        use image = Image.Load<L8>(ms)
+        // Checked crop views require a full trailing row stride, including unused pixels.
+        let pixels = Array.zeroCreate<byte> (image.Width * (image.Height + 1))
+        image.CopyPixelDataTo(pixels)
+        use reader = new ZXingCpp.BarcodeReader()
+        reader.Formats <- ZXingCpp.BarcodeFormats(format)
+        reader.TryHarder <- true
+        reader.TryRotate <- true
+        reader.TryInvert <- false
+        reader.TryDownscale <- true
+        reader.MaxNumberOfSymbols <- 1
+        reader.MinLineCount <- 2
+        reader.ReturnErrors <- false
+        // ImageView borrows the pixel buffer throughout native decoding.
+        use _pin = Memory<byte>(pixels).Pin()
+        let decode x y width height =
+            let offset = y * image.Width + x
+            let length = height * image.Width
+            let region = ReadOnlySpan<byte>(pixels, offset, length)
+            let view = ZXingCpp.ImageView(region, width, height, ZXingCpp.ImageFormat.Lum, image.Width)
+            let results =
+                try reader.From(view)
+                finally GC.KeepAlive(view)
+            try
+                results
+                |> Array.tryPick (fun barcode ->
+                    if barcode.IsValid && not (String.IsNullOrWhiteSpace barcode.Text) then
+                        Some barcode.Text
+                    else
+                        None)
+            finally
+                for barcode in results do
+                    barcode.Dispose()
+
+        let result =
+            match decode 0 0 image.Width image.Height with
+            | Some text -> Some text
+            | None ->
+                let bands = [| 0.0, 0.50; 0.0, 0.60; 0.20, 0.70; 0.30, 0.80; 0.45, 1.0; 0.55, 1.0; 0.65, 1.0 |]
+                [| 0.0; 0.10; 0.20 |]
+                |> Array.tryPick (fun margin ->
+                    bands
+                    |> Array.tryPick (fun (top, bottom) ->
+                        let x = int (Math.Round(float image.Width * margin))
+                        let y = min (image.Height - 1) (int (Math.Round(float image.Height * top)))
+                        let width = image.Width - 2 * x
+                        let height = max 1 (int (Math.Round(float image.Height * bottom)) - y)
+                        decode x y width height))
+        result

src/CouponHubBot/Services/CouponOcrEngine.fs

@@ -213,56 +213,7 @@ type CouponOcrEngine(azureTextOcr: IBotOcr, logger: ILogger<CouponOcrEngine>, ti
     let tryDecodeNative (imageBytes: ReadOnlyMemory<byte>) =
         use activity = botActivity.StartActivity("couponOcr.barcode.native")
         try
-            // Resolve the library before constructing objects with native finalizers.
-            let format = ZXingCpp.BarcodeFormat.Parse("EAN13")
-            use ms = new MemoryStream(imageBytes.ToArray())
-            use image = Image.Load<L8>(ms)
-            let pixels = Array.zeroCreate<byte> (image.Width * image.Height)
-            image.CopyPixelDataTo(pixels)
-            use reader = new ZXingCpp.BarcodeReader()
-            reader.Formats <- ZXingCpp.BarcodeFormats(format)
-            reader.TryHarder <- true
-            reader.TryRotate <- true
-            reader.TryInvert <- false
-            reader.TryDownscale <- true
-            reader.MaxNumberOfSymbols <- 1
-            reader.MinLineCount <- 2
-            reader.ReturnErrors <- false
-            // ImageView borrows the pixel buffer throughout native decoding.
-            use _pin = Memory<byte>(pixels).Pin()
-            let decode x y width height =
-                let offset = y * image.Width + x
-                let length = (height - 1) * image.Width + width
-                let region = ReadOnlySpan<byte>(pixels, offset, length)
-                let view = ZXingCpp.ImageView(region, width, height, ZXingCpp.ImageFormat.Lum, image.Width)
-                let results =
-                    try reader.From(view)
-                    finally GC.KeepAlive(view)
-                try
-                    results
-                    |> Array.tryPick (fun barcode ->
-                        if barcode.IsValid && not (String.IsNullOrWhiteSpace barcode.Text) then
-                            Some barcode.Text
-                        else
-                            None)
-                finally
-                    for barcode in results do
-                        barcode.Dispose()
-
-            let result =
-                match decode 0 0 image.Width image.Height with
-                | Some text -> Some text
-                | None ->
-                    let bands = [| 0.0, 0.50; 0.0, 0.60; 0.20, 0.70; 0.30, 0.80; 0.45, 1.0; 0.55, 1.0; 0.65, 1.0 |]
-                    [| 0.0; 0.10; 0.20 |]
-                    |> Array.tryPick (fun margin ->
-                        bands
-                        |> Array.tryPick (fun (top, bottom) ->
-                            let x = int (Math.Round(float image.Width * margin))
-                            let y = min (image.Height - 1) (int (Math.Round(float image.Height * top)))
-                            let width = image.Width - 2 * x
-                            let height = max 1 (int (Math.Round(float image.Height * bottom)) - y)
-                            decode x y width height))
+            let result = CouponBarcodeReader.tryDecode imageBytes
             if not (isNull activity) then
                 %activity.SetTag("barcode.found", result.IsSome)
             result

tests/CouponHubBot.Ocr.Tests/OcrTests.fs

@@ -223,6 +223,30 @@ type OcrTests(output: ITestOutputHelper) =
             CouponOcrEngine(azure, XUnitLogging.XUnitLogger<CouponOcrEngine>(output, logs), timeProvider)
         engine, http, logs
 
+    [<Theory>]
+    [<InlineData("5_25_2026-01-11_2026-01-17_2706653336241.jpg")>]
+    [<InlineData("5_25_2026-01-20_2026-01-26_2706680353051.jpg")>]
+    [<InlineData("5_25_2026-02-08_2026-02-14_2706726228947.jpg")>]
+    [<InlineData("5_25_2026-04-05_2026-04-15_2706873139950.jpg")>]
+    member _.``Barcode search handles difficult coupon images without failing``(fileName: string) =
+        let bytes = File.ReadAllBytes(Path.Combine(AppContext.BaseDirectory, "Images", fileName))
+        match CouponBarcodeReader.tryDecode(ReadOnlyMemory<byte>(bytes)) with
+        | Some barcode ->
+            let expected = Path.GetFileNameWithoutExtension(fileName).Split('_') |> Array.last
+            Assert.Equal(expected, barcode)
+        | None -> ()
+
+    [<Theory>]
+    [<InlineData(120, 80)>]
+    [<InlineData(960, 1280)>]
+    [<InlineData(1, 1)>]
+    [<InlineData(3, 5)>]
+    member _.``Barcode reader returns no result for a blank image``(width: int, height: int) =
+        use image = new Image<L8>(width, height, L8(255uy))
+        use stream = new MemoryStream()
+        image.SaveAsPng(stream)
+        Assert.Equal(None, CouponBarcodeReader.tryDecode(ReadOnlyMemory<byte>(stream.ToArray())))
+
     [<Theory>]
     [<InlineData(0)>]
     [<InlineData(90)>]