OCR integration

.gitignore

@@ -581,3 +581,5 @@ CHANGELOG.html
 
 # some strange gradle/IntelliJ extension
 extension 'reporting' property 'baseDirectory'
+
+tessdata/

jabgui/src/main/java/org/jabref/gui/fieldeditors/LinkedFilesEditor.java

@@ -325,7 +325,8 @@ private void handleItemMouseClick(LinkedFileViewModel linkedFile, MouseEvent eve
                     bibEntry,
                     viewModel,
                     contextCommandFactory,
-                    multiContextCommandFactory
+                    multiContextCommandFactory,
+                    taskExecutor
             );
 
             ContextMenu contextMenu = contextMenuFactory.createForSelection(listView.getSelectionModel().getSelectedItems());

jabgui/src/main/java/org/jabref/gui/fieldeditors/contextmenu/ContextMenuFactory.java

@@ -2,6 +2,7 @@
 
 import javafx.collections.ObservableList;
 import javafx.scene.control.ContextMenu;
+import javafx.scene.control.MenuItem;
 import javafx.scene.control.SeparatorMenuItem;
 
 import org.jabref.gui.DialogService;
@@ -10,7 +11,10 @@
 import org.jabref.gui.copyfiles.CopySingleFileAction;
 import org.jabref.gui.fieldeditors.LinkedFileViewModel;
 import org.jabref.gui.fieldeditors.LinkedFilesEditorViewModel;
+import org.jabref.gui.linkedfile.OcrAction;
 import org.jabref.gui.preferences.GuiPreferences;
+import org.jabref.logic.l10n.Localization;
+import org.jabref.logic.util.TaskExecutor;
 import org.jabref.model.database.BibDatabaseContext;
 import org.jabref.model.entry.BibEntry;
 
@@ -25,21 +29,24 @@ public class ContextMenuFactory {
     private final LinkedFilesEditorViewModel viewModel;
     private final SingleContextCommandFactory singleCommandFactory;
     private final MultiContextCommandFactory multiCommandFactory;
+    private final TaskExecutor taskExecutor;
 
     public ContextMenuFactory(DialogService dialogService,
                               GuiPreferences preferences,
                               BibDatabaseContext databaseContext,
                               ObservableOptionalValue<BibEntry> bibEntry,
                               LinkedFilesEditorViewModel viewModel,
                               SingleContextCommandFactory singleCommandFactory,
-                              MultiContextCommandFactory multiCommandFactory) {
+                              MultiContextCommandFactory multiCommandFactory,
+                              TaskExecutor taskExecutor) {
         this.dialogService = dialogService;
         this.preferences = preferences;
         this.databaseContext = databaseContext;
         this.bibEntry = bibEntry;
         this.viewModel = viewModel;
         this.singleCommandFactory = singleCommandFactory;
         this.multiCommandFactory = multiCommandFactory;
+        this.taskExecutor = taskExecutor;
     }
 
     public ContextMenu createForSelection(ObservableList<LinkedFileViewModel> selectedFiles) {
@@ -86,9 +93,45 @@ private ContextMenu createContextMenuForFile(LinkedFileViewModel linkedFile) {
                 factory.createMenuItem(StandardActions.DELETE_FILE, singleCommandFactory.build(StandardActions.DELETE_FILE, linkedFile))
         );
 
+        // Add OCR menu item for PDF files
+        if (linkedFile.getFile().getFileType().equalsIgnoreCase("pdf")) {
+            menu.getItems().add(new SeparatorMenuItem());
+
+            MenuItem ocrItem = createOcrMenuItem(linkedFile);
+            menu.getItems().add(ocrItem);
+        }
+
         return menu;
     }
 
+    /**
+     * Creates the OCR menu item for a PDF file.
+     * The menu item is only enabled if the PDF file exists on disk.
+     *
+     * @param linkedFile The linked PDF file
+     * @return MenuItem configured for OCR action
+     */
+    private MenuItem createOcrMenuItem(LinkedFileViewModel linkedFile) {
+        MenuItem ocrItem = new MenuItem(Localization.lang("Extract text (OCR)"));
+
+        // Create the OCR action
+        OcrAction ocrAction = new OcrAction(
+                linkedFile.getFile(),
+                databaseContext,
+                dialogService,
+                preferences.getFilePreferences(),
+                taskExecutor
+        );
+
+        // Set the action to execute when clicked
+        ocrItem.setOnAction(event -> ocrAction.execute());
+
+        // Disable if the action is not executable (file doesn't exist)
+        ocrItem.disableProperty().bind(ocrAction.executableProperty().not());
+
+        return ocrItem;
+    }
+
     @FunctionalInterface
     public interface SingleContextCommandFactory {
         ContextAction build(StandardActions action, LinkedFileViewModel file);

jabgui/src/main/java/org/jabref/gui/linkedfile/OcrAction.java

@@ -0,0 +1,119 @@
+package org.jabref.gui.linkedfile;
+
+import org.jabref.gui.DialogService;
+import org.jabref.gui.StateManager;
+import org.jabref.gui.actions.Action;
+import org.jabref.gui.actions.ActionHelper;
+import org.jabref.gui.actions.SimpleCommand;
+import org.jabref.logic.util.BackgroundTask;
+import org.jabref.logic.util.TaskExecutor;
+import org.jabref.logic.l10n.Localization;
+import org.jabref.logic.ocr.OcrService;
+import org.jabref.logic.ocr.OcrResult;
+import org.jabref.logic.ocr.OcrException;
+import org.jabref.model.database.BibDatabaseContext;
+import org.jabref.model.entry.LinkedFile;
+import org.jabref.logic.FilePreferences;
+
+import java.nio.file.Path;
+import java.util.Optional;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Action for performing OCR (Optical Character Recognition) on linked PDF files.
+ */
+public class OcrAction extends SimpleCommand {
+    private static final Logger LOGGER = LoggerFactory.getLogger(OcrAction.class);
+
+    private final LinkedFile linkedFile;
+    private final BibDatabaseContext databaseContext;
+    private final DialogService dialogService;
+    private final FilePreferences filePreferences;
+    private final TaskExecutor taskExecutor;
+
+    public OcrAction(LinkedFile linkedFile,
+                     BibDatabaseContext databaseContext,
+                     DialogService dialogService,
+                     FilePreferences filePreferences,
+                     TaskExecutor taskExecutor) {
+        this.linkedFile = linkedFile;
+        this.databaseContext = databaseContext;
+        this.dialogService = dialogService;
+        this.filePreferences = filePreferences;
+        this.taskExecutor = taskExecutor;
+
+        // Only executable for existing PDF files
+        this.executable.set(
+                linkedFile.getFileType().equalsIgnoreCase("pdf") &&
+                        linkedFile.findIn(databaseContext, filePreferences).isPresent()
+        );
+    }
+
+    @Override
+    public void execute() {
+        Optional<Path> filePath = linkedFile.findIn(databaseContext, filePreferences);
+
+        if (filePath.isEmpty()) {
+            dialogService.showErrorDialogAndWait(
+                    Localization.lang("File not found"),
+                    Localization.lang("Could not locate the PDF file on disk.")
+            );
+            return;
+        }
+
+        dialogService.notify(Localization.lang("Performing OCR..."));
+
+        BackgroundTask<OcrResult> task = BackgroundTask.wrap(() -> {
+                                                           try {
+                                                               OcrService ocrService = new OcrService();
+                                                               return ocrService.performOcr(filePath.get());
+                                                           } catch (OcrException e) {
+                                                               // This is a bug in JabRef
+                                                               LOGGER.error("Failed to initialize OCR service", e);
+                                                               return OcrResult.failure("OCR service initialization failed: " + e.getMessage());
+                                                           }
+                                                       })
+                                                       .showToUser(true)  // Show in task list
+                                                       .withInitialMessage(Localization.lang("Performing OCR on %0", linkedFile.getLink()));
+
+        task.onSuccess(result -> {
+                // Use pattern matching with the sealed class
+                switch (result) {
+                    case OcrResult.Success success -> {
+                        String extractedText = success.text();
+                        if (extractedText.isEmpty()) {
+                            dialogService.showInformationDialogAndWait(
+                                    Localization.lang("OCR Complete"),
+                                    Localization.lang("No text was found in the PDF.")
+                            );
+                        } else {
+                            // Show preview
+                            String preview = extractedText.length() > 1000
+                                    ? extractedText.substring(0, 1000) + "..."
+                                    : extractedText;
+
+                            dialogService.showInformationDialogAndWait(
+                                    Localization.lang("OCR Result"),
+                                    preview
+                            );
+                        }
+                    }
+                    case OcrResult.Failure failure -> {
+                        dialogService.showErrorDialogAndWait(
+                                Localization.lang("OCR failed"),
+                                failure.errorMessage()
+                        );
+                    }
+                }
+            })
+            .onFailure(exception -> {
+                dialogService.showErrorDialogAndWait(
+                        Localization.lang("OCR failed"),
+                        exception.getMessage()
+                );
+            })
+            .executeWith(taskExecutor);
+    }
+}

jabgui/src/test/java/org/jabref/gui/fieldeditors/contextmenu/ContextMenuFactoryTest.java

@@ -11,6 +11,7 @@
 import org.jabref.gui.fieldeditors.LinkedFileViewModel;
 import org.jabref.gui.fieldeditors.LinkedFilesEditorViewModel;
 import org.jabref.gui.preferences.GuiPreferences;
+import org.jabref.logic.util.TaskExecutor;
 import org.jabref.model.database.BibDatabaseContext;
 import org.jabref.model.entry.BibEntry;
 import org.jabref.model.entry.LinkedFile;
@@ -41,6 +42,7 @@ public class ContextMenuFactoryTest {
     private ContextMenuFactory factory;
     private ContextMenuFactory.SingleContextCommandFactory singleCommandFactory;
     private ContextMenuFactory.MultiContextCommandFactory multiCommandFactory;
+    private TaskExecutor taskExecutor;
 
     @BeforeAll
     public static void initToolkit() {
@@ -78,7 +80,8 @@ public void setUp() {
                 bibEntry,
                 viewModel,
                 singleCommandFactory,
-                multiCommandFactory
+                multiCommandFactory,
+                taskExecutor
         );
     }
 

jablib/build.gradle.kts

@@ -253,6 +253,9 @@ dependencies {
     // Required for LocalizationConsistencyTest
     testImplementation("org.testfx:testfx-core:4.0.16-alpha")
     testImplementation("org.testfx:testfx-junit5:4.0.16-alpha")
+
+    // OCR support
+    implementation("net.sourceforge.tess4j:tess4j:5.15.0")
 }
 /*
 jacoco {

jablib/src/main/java/module-info.java

@@ -105,6 +105,7 @@
     exports org.jabref.logic.crawler;
     exports org.jabref.logic.git;
     exports org.jabref.logic.pseudonymization;
+    exports org.jabref.logic.ocr;
     exports org.jabref.logic.citation.repository;
 
     requires java.base;
@@ -252,5 +253,6 @@
     requires mslinks;
     requires org.antlr.antlr4.runtime;
     requires org.libreoffice.uno;
+    requires tess4j;
     // endregion
 }

jablib/src/main/java/org/jabref/logic/ocr/OcrException.java

@@ -0,0 +1,28 @@
+package org.jabref.logic.ocr;
+
+/**
+ * Exception thrown when OCR operations fail.
+ * This exception wraps lower-level OCR engine exceptions to provide
+ * a consistent interface for error handling throughout JabRef.
+ */
+public class OcrException extends Exception {
+
+    /**
+     * Constructs an OcrException with a message and underlying cause.
+     *
+     * @param message Descriptive error message
+     * @param cause The underlying exception that caused this error
+     */
+    public OcrException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    /**
+     * Constructs an OcrException with only a message.
+     *
+     * @param message Descriptive error message
+     */
+    public OcrException(String message) {
+        super(message);
+    }
+}

jablib/src/main/java/org/jabref/logic/ocr/OcrResult.java

@@ -0,0 +1,60 @@
+package org.jabref.logic.ocr;
+
+/**
+ * Represents the result of an OCR operation.
+ * Uses sealed classes to ensure type safety and avoid null parameters.
+ */
+public sealed interface OcrResult {
+
+    /**
+     * Represents a successful OCR operation with extracted text.
+     */
+    record Success(String text) implements OcrResult {
+        public Success {
+            // Convert null to empty string instead of throwing exception
+            if (text == null) {
+                text = "";
+            }
+        }
+    }
+
+    /**
+     * Represents a failed OCR operation with an error message.
+     */
+    record Failure(String errorMessage) implements OcrResult {
+        public Failure {
+            // Provide default message instead of throwing exception
+            if (errorMessage == null || errorMessage.isBlank()) {
+                errorMessage = "Unknown error occurred";
+            }
+        }
+    }
+
+    /**
+     * Checks if this result represents a success.
+     */
+    default boolean isSuccess() {
+        return this instanceof Success;
+    }
+
+    /**
+     * Checks if this result represents a failure.
+     */
+    default boolean isFailure() {
+        return this instanceof Failure;
+    }
+
+    /**
+     * Factory method for creating a success result.
+     */
+    static OcrResult success(String text) {
+        return new Success(text);
+    }
+
+    /**
+     * Factory method for creating a failure result.
+     */
+    static OcrResult failure(String errorMessage) {
+        return new Failure(errorMessage);
+    }
+}