Fix memory leak in pdfOCR

DEVSIX-8683

Author: vitali-pr

pdfocr-tesseract4/src/main/java/com/itextpdf/pdfocr/tesseract4/ImagePreprocessingUtil.java

@@ -137,7 +137,9 @@ static BufferedImage readAsPixAndConvertToBufferedImage(
             final File inputImage)
             throws IOException {
         Pix pix = TesseractOcrUtil.readPixFromFile(inputImage);
-        return TesseractOcrUtil.convertPixToImage(pix);
+        BufferedImage img = TesseractOcrUtil.convertPixToImage(pix);
+        TesseractOcrUtil.destroyPix(pix);
+        return img;
     }
 
     /**
@@ -155,7 +157,7 @@ static Pix preprocessImage(final File inputFile,
                                final int pageNumber,
                                final ImagePreprocessingOptions imagePreprocessingOptions)
             throws PdfOcrTesseract4Exception {
-        Pix pix = null;
+        Pix pix;
         // read image
         if (isTiffImage(inputFile)) {
             pix = TesseractOcrUtil.readPixPageFromTiff(inputFile,
@@ -168,7 +170,11 @@ static Pix preprocessImage(final File inputFile,
                     PdfOcrTesseract4ExceptionMessageConstant.CANNOT_READ_PROVIDED_IMAGE)
                     .setMessageParams(inputFile.getAbsolutePath());
         }
-        return TesseractOcrUtil.preprocessPix(pix, imagePreprocessingOptions);
+        Pix preprocessedPix = TesseractOcrUtil.preprocessPix(pix, imagePreprocessingOptions);
+        if (!TesseractOcrUtil.samePix(pix, preprocessedPix)) {
+            TesseractOcrUtil.destroyPix(pix);
+        }
+        return preprocessedPix;
     }
 
     /**

pdfocr-tesseract4/src/main/java/com/itextpdf/pdfocr/tesseract4/LeptonicaWrapper.java

@@ -89,6 +89,14 @@ public static void lept_free(Pointer pointer) {
         Leptonica1.lept_free(pointer);
     }
 
+    public static void pixFreeData(Pix pix) {
+        if (JDK_MAJOR_VERSION < LEPTONICA_NOT_SUPPORTED_JDK_VERSION) {
+            Leptonica.INSTANCE.pixFreeData(pix);
+            return;
+        }
+        Leptonica1.pixFreeData(pix);
+    }
+
     public static void pixWriteMem(PointerByReference pointer, NativeSizeByReference nativeSize, Pix pix, int i) {
         if (JDK_MAJOR_VERSION < LEPTONICA_NOT_SUPPORTED_JDK_VERSION) {
             Leptonica.INSTANCE.pixWriteMem(pointer, nativeSize, pix, i);

pdfocr-tesseract4/src/main/java/com/itextpdf/pdfocr/tesseract4/Tesseract4ExecutableOcrEngine.java

@@ -427,6 +427,7 @@ private String preprocessImage(final File inputImage,
                                 img);
                     }
                 }
+                TesseractOcrUtil.destroyPix(pix);
             }
             if (!getTesseract4OcrEngineProperties().isPreprocessingImages()
                     || !Files.exists(Paths.get(tmpFileName))) {

pdfocr-tesseract4/src/main/java/com/itextpdf/pdfocr/tesseract4/Tesseract4LibOcrEngine.java

@@ -45,6 +45,7 @@ This file is part of the iText (R) project.
 import com.itextpdf.pdfocr.tesseract4.exceptions.PdfOcrInputTesseract4Exception;
 import com.itextpdf.pdfocr.tesseract4.logs.Tesseract4LogMessageConstant;
 
+import net.sourceforge.lept4j.Pix;
 import net.sourceforge.tess4j.ITesseract;
 import net.sourceforge.tess4j.TesseractException;
 import org.slf4j.LoggerFactory;
@@ -309,12 +310,14 @@ private String getOcrResultForSinglePage(final File inputImage,
             // preprocess if required
             if (getTesseract4OcrEngineProperties().isPreprocessingImages()) {
                 // preprocess and try to ocr
+                Pix pix = ImagePreprocessingUtil
+                        .preprocessImage(inputImage, pageNumber,
+                                getTesseract4OcrEngineProperties().getImagePreprocessingOptions());
                 result = new TesseractOcrUtil().getOcrResultAsString(
                         getTesseractInstance(),
-                        ImagePreprocessingUtil
-                                .preprocessImage(inputImage, pageNumber,
-                                        getTesseract4OcrEngineProperties().getImagePreprocessingOptions()),
+                        pix,
                         outputFormat);
+                TesseractOcrUtil.destroyPix(pix);
             }
             if (result == null) {
                 BufferedImage bufferedImage = ImagePreprocessingUtil

pdfocr-tesseract4/src/main/java/com/itextpdf/pdfocr/tesseract4/TesseractOcrUtil.java

@@ -135,8 +135,14 @@ static Pix readPixPageFromTiff(final File inputFile,
     static Pix preprocessPix(final Pix pix,
                              final ImagePreprocessingOptions imagePreprocessingOptions) {
         Pix pix1 = convertToGrayscale(pix);
-        pix1 = otsuImageThresholding(pix1, imagePreprocessingOptions);
-        return pix1;
+        Pix pix2 = otsuImageThresholding(pix1, imagePreprocessingOptions);
+        if (!TesseractOcrUtil.samePix(pix, pix1) && !TesseractOcrUtil.samePix(pix1, pix2)) {
+            // pix1 is cleaned only if it's unique here.
+            // If it points to the same memory as pix then it should be cleaned higher in the call stack.
+            // If it points to the same memory as pix2 then it is still required.
+            TesseractOcrUtil.destroyPix(pix1);
+        }
+        return pix2;
     }
 
     /**
@@ -175,7 +181,6 @@ static Pix convertToGrayscale(final Pix pix) {
     static Pix otsuImageThresholding(final Pix inputPix,
                                      final ImagePreprocessingOptions imagePreprocessingOptions) {
         if (inputPix != null) {
-            Pix binarizedPix = null;
             if (inputPix.d == 8) {
                 PointerByReference pointer = new PointerByReference();
                 LeptonicaWrapper
@@ -189,18 +194,16 @@ static Pix otsuImageThresholding(final Pix inputPix,
                                 getOtsuAdaptiveThresholdSmoothingTileSize(inputPix.h,
                                         imagePreprocessingOptions.isSmoothTiling()),
                                 0,null, pointer);
-                binarizedPix = new Pix(pointer.getValue());
+                Pix binarizedPix = new Pix(pointer.getValue());
                 if (binarizedPix.w > 0 && binarizedPix.h > 0) {
-                    // destroying original pix
-                    destroyPix(inputPix);
                     return binarizedPix;
                 } else {
                     final String logMessage = MessageFormatUtil.format(
                             Tesseract4LogMessageConstant.CANNOT_BINARIZE_IMAGE,
                             inputPix.d);
                     LOGGER.info(logMessage);
                     // destroying created PointerByReference object
-                    destroyPix(binarizedPix);
+                    TesseractOcrUtil.destroyPix(binarizedPix);
                     return inputPix;
                 }
             } else {
@@ -251,8 +254,27 @@ static int getImagePixelColor(BufferedImage image, int x, int y) {
      */
     static void destroyPix(Pix inputPix) {
         if (inputPix != null) {
-            LeptonicaWrapper.lept_free(inputPix.getPointer());
+            LeptonicaWrapper.pixFreeData(inputPix);
+        }
+    }
+
+    /**
+     * Checks whether two {@link Pix} objects refer to the same content.
+     *
+     * @param pix1 the object to compare
+     * @param pix2 the object to compare
+     * @return {@code true} if objects refer to the same content, {@code false} otherwise
+     */
+    static boolean samePix(Pix pix1, Pix pix2) {
+        if (pix1 == pix2) {
+            return true;
+        }
+        if (pix1 == null || pix2 == null) {
+            return false;
         }
+
+        // Both not null
+        return pix1.getPointer().equals(pix2.getPointer());
     }
 
     /**
@@ -668,7 +690,11 @@ static Pix readPix(final byte[] imageBytes) {
         }
         if (pix != null) {
             int rotation = detectRotation(imageBytes);
-            pix = rotate(pix, rotation);
+            Pix rotatedPix = rotate(pix, rotation);
+            if (!TesseractOcrUtil.samePix(rotatedPix, pix)) {
+                TesseractOcrUtil.destroyPix(pix);
+            }
+            pix = rotatedPix;
         }
         return pix;
     }
@@ -801,7 +827,7 @@ static ImageData applyRotation(final ImageData imageData) {
                     );
                 }
             } finally {
-                destroyPix(pix);
+                TesseractOcrUtil.destroyPix(pix);
             }
             return newImageData;
         }

pdfocr-tesseract4/src/test/java/com/itextpdf/pdfocr/tesseract4/ImagePreprocessingUtilTest.java

@@ -34,6 +34,7 @@ This file is part of the iText (R) project.
 import java.io.File;
 import java.io.IOException;
 
+import net.sourceforge.lept4j.Pix;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
@@ -63,32 +64,32 @@ public void testImagePreprocessingOptions() throws IOException {
         String processedImg = getTargetDirectory() + "thai_02_processed.jpg";
         String compareImg = TEST_IMAGES_DIRECTORY + "thai_02_cmp_01.jpg";
 
-        TesseractOcrUtil.savePixToPngFile(processedImg,
-                ImagePreprocessingUtil.preprocessImage(new File(sourceImg),
-                        1,
-                        new ImagePreprocessingOptions())
-        );
+        Pix pix = ImagePreprocessingUtil.preprocessImage(new File(sourceImg),
+                1,
+                new ImagePreprocessingOptions());
+        TesseractOcrUtil.savePixToPngFile(processedImg, pix);
+        TesseractOcrUtil.destroyPix(pix);
         compareImagesWithPrecision(compareImg, processedImg, 0.1);
 
         compareImg = TEST_IMAGES_DIRECTORY + "thai_02_cmp_02.jpg";
-        TesseractOcrUtil.savePixToPngFile(processedImg,
-                ImagePreprocessingUtil.preprocessImage(new File(sourceImg),
-                        1,
-                        new ImagePreprocessingOptions()
-                                .setTileWidth(300)
-                                .setTileHeight(300))
-        );
+        pix = ImagePreprocessingUtil.preprocessImage(new File(sourceImg),
+                1,
+                new ImagePreprocessingOptions()
+                        .setTileWidth(300)
+                        .setTileHeight(300));
+        TesseractOcrUtil.savePixToPngFile(processedImg, pix);
+        TesseractOcrUtil.destroyPix(pix);
         compareImagesWithPrecision(compareImg, processedImg, 0.1);
 
         compareImg = TEST_IMAGES_DIRECTORY + "thai_02_cmp_03.jpg";
-        TesseractOcrUtil.savePixToPngFile(processedImg,
-                ImagePreprocessingUtil.preprocessImage(new File(sourceImg),
-                        1,
-                        new ImagePreprocessingOptions()
-                                .setTileWidth(300)
-                                .setTileHeight(300)
-                                .setSmoothTiling(false))
-        );
+        pix = ImagePreprocessingUtil.preprocessImage(new File(sourceImg),
+                1,
+                new ImagePreprocessingOptions()
+                        .setTileWidth(300)
+                        .setTileHeight(300)
+                        .setSmoothTiling(false));
+        TesseractOcrUtil.savePixToPngFile(processedImg, pix);
+        TesseractOcrUtil.destroyPix(pix);
         compareImagesWithPrecision(compareImg, processedImg, 0.1);
     }
 

pdfocr-tesseract4/src/test/java/com/itextpdf/pdfocr/tesseract4/TesseractOcrUtilTest.java

@@ -61,6 +61,7 @@ public void testTesseract4OcrForPix()
         String result = new TesseractOcrUtil().getOcrResultAsString(
                 tesseract4LibOcrEngine.getTesseractInstance(),
                 pix, OutputFormat.TXT);
+        TesseractOcrUtil.destroyPix(pix);
         Assertions.assertTrue(result.contains(expected));
     }
 
@@ -182,6 +183,7 @@ public void testPixSavingAsPng() {
         Assertions.assertFalse(Files.exists(Paths.get(tmpFileName)));
         Pix pix = TesseractOcrUtil.readPix(new File(path));
         TesseractOcrUtil.savePixToPngFile(tmpFileName, pix);
+        TesseractOcrUtil.destroyPix(pix);
         Assertions.assertTrue(Files.exists(Paths.get(tmpFileName)));
         TesseractHelper.deleteFile(tmpFileName);
         Assertions.assertFalse(Files.exists(Paths.get(tmpFileName)));