Exclude source folder from derivative generation

Kitodo/src/main/java/org/kitodo/production/services/image/ImageGenerator.java

@@ -112,7 +112,9 @@ public class ImageGenerator implements Runnable {
     public ImageGenerator(Subfolder sourceFolder, GenerationMode mode, Collection<Subfolder> outputs) {
         this.sourceFolder = sourceFolder;
         this.mode = mode;
-        this.outputs = outputs;
+        this.outputs = outputs.stream()
+            .filter(output -> !isSourceFolder(output))
+            .toList();
         this.state = ImageGeneratorStep.LIST_SOURCE_FOLDER;
         this.sources = Collections.emptyList();
         this.contentToBeGenerated = new LinkedList<>();
@@ -133,6 +135,27 @@ public void removeGeneratedContent() {
         }
     }
 
+    /**
+     * Returns whether the given subfolder represents the configured source folder.
+     * The contents of the source folder must never be regenerated.
+     *
+     * @param subfolder
+     *            subfolder to check
+     * @return whether the subfolder is the configured source folder
+     */
+    private boolean isSourceFolder(Subfolder subfolder) {
+        Folder source = sourceFolder.getFolder();
+        Folder output = subfolder.getFolder();
+
+        if (source == output) {
+            return true;
+        }
+
+        return Objects.nonNull(source.getId())
+            && Objects.nonNull(output.getId())
+            && Objects.equals(source.getId(), output.getId());
+    }
+
     /**
      * Appends the element to the list of elements to be generated.
      *

Kitodo/src/test/java/org/kitodo/production/services/image/ImageGeneratorIT.java

@@ -424,4 +424,41 @@ public void testRecreatingAllMissingOrDamagedImagesForFilesInTheSameFolder() thr
         assertNotEquals(resultFileTwoBefore, lastModifiedTime(mixedResultTwo), mixedResultTwo + MESSAGE_NOT_CHANGED);
         assertNotEquals(resultFileThreeBefore, lastModifiedTime(mixedResultThree), mixedResultThree + MESSAGE_NOT_CHANGED);
     }
+
+    /**
+     * Verifies that the configured source folder is ignored when it is also
+     * supplied as an output folder.
+     */
+    @Test
+    public void testSourceFolderIsNotRegenerated() throws Exception {
+        Process process = new Process();
+        process.setId(processId);
+        process.setTitle(processTitle);
+
+        Folder folder = new Folder();
+        folder.setPath(tiffFolder);
+        folder.setMimeType(tiffType);
+        folder.setDerivative(1.0);
+
+        Subfolder sourceFolder = new Subfolder(process, folder);
+        VariableReplacer variableReplacer = new MockVariableReplacer(processTitle);
+        setField(sourceFolder, "variableReplacer", variableReplacer);
+
+        Subfolder outputFolder = new Subfolder(process, folder);
+        setField(outputFolder, "variableReplacer", variableReplacer);
+
+        Collection<Subfolder> outputs = Collections.singletonList(outputFolder);
+        // Intentionally use the same Folder configuration for source and output.
+        ImageGenerator imageGenerator = new ImageGenerator(sourceFolder, GenerationMode.ALL, outputs);
+
+        Optional<FileTime> inputFileOneBefore = lastModifiedTime(inputFileOne);
+        Optional<FileTime> inputFileTwoBefore = lastModifiedTime(inputFileTwo);
+        Optional<FileTime> inputFileThreeBefore = lastModifiedTime(inputFileThree);
+
+        imageGenerator.run();
+
+        assertEquals(inputFileOneBefore, lastModifiedTime(inputFileOne), inputFileOne + MESSAGE_CHANGED);
+        assertEquals(inputFileTwoBefore, lastModifiedTime(inputFileTwo), inputFileTwo + MESSAGE_CHANGED);
+        assertEquals(inputFileThreeBefore, lastModifiedTime(inputFileThree), inputFileThree + MESSAGE_CHANGED);
+    }
 }