Fix #38

README.md

@@ -48,7 +48,7 @@ dotnet add package TesseractOcrMaui
 3. By package reference
 
 ```xml
-<PackageReference Include="TesseractOcrMaui" Version="1.1.0" />
+<PackageReference Include="TesseractOcrMaui" Version="1.1.6" />
 ```
 
 ### 2. Add package to dependency injection (see TesseractOcrMauiTestApp)

TesseractOcrMaui.IOS/Properties/README.md

@@ -13,13 +13,13 @@ This package `TesseractOcrMaui.IOS` only includes bindings for iOS and should no
 2. Package reference
 
 ```xml
-<PackageReference Include="TesseractOcrMaui" Version="1.1.0" />
+<PackageReference Include="TesseractOcrMaui" Version="1.1.6" />
 ```
 
 3. Dotnet CLI
 
 ```ps
-dotnet add package TesseractOcrMaui --version 1.1.0
+dotnet add package TesseractOcrMaui --version 1.1.6
 ```
 
 Note that you should check what the current package version is and use it in your command.

TesseractOcrMaui.IOS/TesseractApi.cs

@@ -11,6 +11,18 @@ public sealed partial class TesseractApi
 
     const CharSet StrEncoding = CharSet.Ansi;
 
+    [LibraryImport(DllName, EntryPoint = "TessDeleteTextArray")]
+    [UnmanagedCallConv(CallConvs = new Type[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
+    public static unsafe partial void DeleteStringArray(char** ptr);
+
+    [LibraryImport(DllName, EntryPoint = "TessDeleteIntArray")]
+    [UnmanagedCallConv(CallConvs = new Type[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
+    public static partial void DeleteIntArray(IntPtr ptr);
+
+    [LibraryImport(DllName, EntryPoint = "TessDeleteText")]
+    [UnmanagedCallConv(CallConvs = new Type[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
+    public static partial void DeleteString(IntPtr ptr);
+
     [LibraryImport(DllName, EntryPoint = "TessBaseAPICreate")]
     [UnmanagedCallConv(CallConvs = new Type[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
     public static partial IntPtr CreateApi();
@@ -36,9 +48,14 @@ public extern static int BaseApi5Init(HandleRef handle, string datapath, int dat
 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPISetImage2")]
     public static extern void SetImage(HandleRef handle, HandleRef pixHandle);
-
+
+    // This does not work with non acsii characters, use GetUTF8Text_Ptr instead 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPIGetUTF8Text", CharSet = StrEncoding)]
-    public static extern string GetUTF8Text(HandleRef handle);
+    public static extern string GetUTF8Text(HandleRef handle);  
+
+    // Remember to delete string after copying, use DeleteString(IntPtr ptr)
+    [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPIGetUTF8Text")]
+    public static extern IntPtr GetUTF8Text_Ptr(HandleRef handle);
 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPIAllWordConfidences")]
     public static extern int[] GetConfidences(HandleRef handle);

TesseractOcrMaui.IOS/TesseractOcrMaui.IOS.csproj

@@ -50,7 +50,7 @@
 
 	<!-- Package properties -->
 	<PropertyGroup>
-		<Version>1.0.5</Version>
+		<Version>1.0.6</Version>
 		<Title>Maui Tesseract ocr iOS bindings</Title>
 		<PackageId>TesseractOcrMaui.IOS</PackageId>
 		<Authors>henrivain</Authors>

TesseractOcrMaui/Enums/RecognizionStatus.cs

@@ -19,5 +19,6 @@ public enum RecognizionStatus
     InvalidImage,
     ImageAlredyProcessed,
     CannotRecognizeText,
-    TessDataFolderNotProvided
+    TessDataFolderNotProvided,
+    InvalidResultString
 }

TesseractOcrMaui/Exceptions/PageNotDisposedException.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TesseractOcrMaui.Exceptions;
+
+/// <summary>
+/// Exception thrown when multiple images are given to TessEngine at the same time.
+/// Old TessPage must be disposed before trying to process new image.
+/// </summary>
+public class PageNotDisposedException : TesseractException
+{
+    /// <summary>
+    /// New exception thrown when multiple images are given to TessEngine at the same time.
+    /// Old TessPage must be disposed before trying to process new image.
+    /// </summary>
+    public PageNotDisposedException() { }
+
+    /// <summary>
+    /// New exception with message thrown when multiple images are given to TessEngine at the same time.
+    /// Old TessPage must be disposed before trying to process new image.
+    /// </summary>
+    /// <param name="message">Error reason</param>
+    public PageNotDisposedException(string message) : base(message) { }
+
+    /// <summary>
+    /// New exception with message and inner exception thrown when multiple images are given to TessEngine at the same time.
+    /// Old TessPage must be disposed before trying to process new image.
+    /// </summary>
+    /// <param name="message">Error reason</param>
+    /// <param name="innerException">Exception that caused this exception</param>
+    public PageNotDisposedException(string message, Exception innerException) 
+        : base(message, innerException) { }
+}

TesseractOcrMaui/Exceptions/StringMarshallingException.cs

@@ -0,0 +1,29 @@
+namespace TesseractOcrMaui.Exceptions;
+
+/// <summary>
+/// Exception thrown when library cannot marshal string returned from native library correctly.
+/// </summary>
+public class StringMarshallingException : TesseractException
+{
+    /// <summary>
+    /// New Exception thrown when library cannot marshal string returned from native library correctly.
+    /// </summary>
+    public StringMarshallingException() : base() { }
+
+    /// <summary>
+    /// New Exception with message thrown when library cannot marshal string returned from native library correctly.
+    /// </summary>
+    /// <param name="message">Error reason.</param>
+    public StringMarshallingException(string? message) : base(message) { }
+
+    /// <summary>
+    /// New Exception with message and inner exception. 
+    /// Thrown when library cannot marshal string returned from native library correctly.
+    /// </summary>
+    /// <param name="message">Error reason.</param>
+    /// <param name="innerException">Exception that caused this error.</param>
+    public StringMarshallingException(string? message, Exception? innerException) : base(message, innerException)
+    {
+    }
+
+}

TesseractOcrMaui/ImportApis/TesseractApi.cs

@@ -19,9 +19,14 @@ internal sealed partial class TesseractApi
     const string DllName = "Use Windows, Android or iOS Platform";
 #endif
 
-
     const CharSet StrEncoding = CharSet.Ansi;
 
+
+
+    [LibraryImport(DllName, EntryPoint = "TessDeleteText")]
+    [UnmanagedCallConv(CallConvs = new Type[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
+    public static partial void DeleteString(IntPtr ptr);
+
     [LibraryImport(DllName, EntryPoint = "TessBaseAPICreate")]
     [UnmanagedCallConv(CallConvs = new Type[] { typeof(System.Runtime.CompilerServices.CallConvCdecl) })]
     public static partial IntPtr CreateApi();
@@ -47,10 +52,15 @@ public extern static int BaseApi5Init(HandleRef handle, string datapath, int dat
 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPISetImage2")]
     public static extern void SetImage(HandleRef handle, HandleRef pixHandle);
-
+
+    // This does not work with non acsii characters, use GetUTF8Text_Ptr instead 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPIGetUTF8Text", CharSet = StrEncoding)]
     public static extern string GetUTF8Text(HandleRef handle);
 
+    // Remember to delete string after copying, use DeleteString(IntPtr ptr)
+    [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPIGetUTF8Text")]
+    public static extern IntPtr GetUTF8Text_Ptr(HandleRef handle);
+
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl, EntryPoint = "TessBaseAPIAllWordConfidences")]
     public static extern int[] GetConfidences(HandleRef handle);
 

TesseractOcrMaui/Results/RecognizionResult.cs

@@ -20,6 +20,11 @@ public RecognizionResult() { }
     /// </summary>
     public string? Message { get; init; }
 
+    /// <summary>
+    /// Optional exception that was thrown if failed.
+    /// </summary>
+    public Exception? Exception { get; init; }
+
     /// <summary>
     /// Recognized text from the image.
     /// </summary>

TesseractOcrMaui/TessEngine.cs

@@ -98,11 +98,9 @@ public TessEngine(string languages, string traineddataPath, EngineMode mode,
     /// <returns>New Tess page containing information for recognizion.</returns>
     /// <exception cref="ArgumentNullException">image is null.</exception>
     /// <exception cref="ArgumentException">Image width or height has invalid values.</exception>
-    /// <exception cref="InvalidOperationException">Image already processed. You must dispose page after using.</exception>
-    public TessPage ProcessImage(Pix image, PageSegmentationMode? mode = null)
-    {
-        return ProcessImage(image, null, new Rect(0, 0, image.Width, image.Height), mode);
-    }
+    /// <exception cref="PageNotDisposedException">Image already processed. You must dispose page after using.</exception>
+    public TessPage ProcessImage(Pix image, PageSegmentationMode? mode = null) 
+        => ProcessImage(image, null, new Rect(0, 0, image.Width, image.Height), mode);
 
     /// <summary>
     /// Process image to TessPage.
@@ -114,7 +112,7 @@ public TessPage ProcessImage(Pix image, PageSegmentationMode? mode = null)
     /// <returns>New Tess page containing information for recognizion.</returns>
     /// <exception cref="ArgumentNullException">image is null.</exception>
     /// <exception cref="ArgumentException">Region is out of bounds.</exception>
-    /// <exception cref="InvalidOperationException">Image already processed. You must dispose page after using.</exception>
+    /// <exception cref="PageNotDisposedException">Image already processed. You must dispose page after using.</exception>
     public TessPage ProcessImage(Pix image, string? inputName, Rect region, PageSegmentationMode? mode)
     {
         if (image is null)
@@ -130,10 +128,9 @@ public TessPage ProcessImage(Pix image, string? inputName, Rect region, PageSegm
         }
         if (_processCount > 0)
         {
-            _logger.LogError("{cls}: Tried to process image with engine that already has one. " +
-                "You must dispose image after using.", nameof(TessEngine));
-            throw new InvalidOperationException("One image already set. " +
-                "You must dispose page after using.");
+            _logger.LogError("{cls}: Already has one image process. You must dispose {page} after using it.", 
+                nameof(TessEngine), nameof(TessPage));
+            throw new PageNotDisposedException("You must dispose old TessPage after using it.");
         }
 
         _processCount++;

TesseractOcrMaui/TessPage.cs

@@ -75,44 +75,39 @@ public TessPage(TessEngine engine, Pix image, string? inputName, Rect region, Pa
     /// <summary>
     /// Get text from image. Runs recognizion if it is not already done. Uses UTF-8.
     /// </summary>
-    /// <returns>Text that apprears in image.</returns>
+    /// <returns>Recognized text as UTF-8 string</returns>
     /// <exception cref="InvalidOperationException">PageSegmentationMode is OsdOnly when recognizing.</exception>
     /// <exception cref="ImageRecognizionException">Native Library call returns failed status when recognizing.</exception>
     /// <exception cref="TesseractException">Can't get thresholded image when recognizing.</exception>
-    /// <exception cref="InvalidBytesException">[WINDOWS] Invalid byte sequence in string.</exception>
+    /// <exception cref="StringMarshallingException">
+    /// When recognizion result string pointer is nullpointer or the pointer cannot 
+    /// be marshalled into UTF-8 string.
+    /// </exception>
     public string GetText()
     {
         Logger.LogInformation("Try to get text from image.");
 
         Recognize();
 
-        string result = TesseractApi.GetUTF8Text(Engine.Handle);
-
-        Logger.LogInformation("Found '{count}' characters in image.", result.Length);
-
-        // My Windows seems to use different encoding than UTF-8 by default, so this should help.
-        // Android uses UTF-8 as default so all good.
-#if WINDOWS
-        var bytes = new byte[result.Length];
-        for (int i = 0; i < result.Length; i++)
-        {
-            bytes[i] = (byte)result[i];
-        }
-        if (bytes is null)
-        {
-            return string.Empty;
-        }
-        try
+        IntPtr ptr = TesseractApi.GetUTF8Text_Ptr(Engine.Handle);
+        if (ptr == IntPtr.Zero)
         {
-            return Encoding.UTF8.GetString(bytes);
+            Logger.LogError("Recognizion result string cannot be marshalled from null pointer.");
+            throw new StringMarshallingException("String cannot be marshalled from null pointer.");
         }
-        catch (Exception ex)
+
+        string? result = Marshal.PtrToStringUTF8(ptr);
+        TesseractApi.DeleteString(ptr);
+
+        if (result is null)
         {
-            throw new InvalidBytesException("Cannot encode current byte array, because it contains invalid bytes.", ex);
+            Logger.LogError("Cannot encode char* to UTF-8 string.");
+            throw new StringMarshallingException("Could not encode recognizion result string to UTF-8.");
         }
-#else
+
+        Logger.LogInformation("Found '{count}' characters in image.", result.Length);
+
         return result;
-#endif
     }
 
     /// <summary>