memory optimisations

src/main/java/com/iqser/red/pdftronlogic/commons/ClippingPathStack.java

@@ -1,7 +1,5 @@
 package com.iqser.red.pdftronlogic.commons;
 
-
-
 import static com.iqser.red.pdftronlogic.commons.InvisibleElementRemovalService.TOLERANCE;
 
 import java.awt.geom.Area;
@@ -35,6 +33,13 @@ public class ClippingPathStack {
     }
 
 
+    @SneakyThrows
+    public void intersectClippingPath(Rectangle2D path) {
+
+        getCurrentClippingPath().intersect(new Area(path));
+    }
+
+
     public boolean almostIntersects(double x, double y, double width, double height) {
         // To address inconsistencies in the calculation of the bounding box we slightly increase the rectangle
         // Height or width are zero for straight lines, even though they are being rendered. Therefore, height or width must be at minimum >0.
@@ -56,15 +61,16 @@ public class ClippingPathStack {
     public void enterNewGState() {
 
         Area current = stack.peek();
-        Area cloned = new Area();
+        Area cloned = (Area) current.clone();
-        cloned.add(current);
         stack.push(cloned);
     }
 
 
     public void leaveGState() {
 
-        stack.pop();
+        // somehow this greatly helps memory management
+        var popped = stack.pop();
+        popped.reset();
     }
 
 }

src/main/java/com/iqser/red/pdftronlogic/commons/ElementFeatureFactory.java

@@ -4,6 +4,7 @@ import com.pdftron.common.PDFNetException;
 import com.pdftron.pdf.Element;
 
 public class ElementFeatureFactory {
+
     public static ElementFeatures extractFeatures(Element element) throws PDFNetException {
 
         return switch (element.getType()) {
@@ -16,7 +17,9 @@ public class ElementFeatureFactory {
         };
     }
 
+
     public static ElementFeatures extractFeaturesWithHash(Element element, String hashObject) throws PDFNetException {
+
         return buildImage(element)
                 .hashOfImage(hashObject)
                 .build();
@@ -25,20 +28,23 @@ public class ElementFeatureFactory {
 
     private static ElementFeatures.Form buildForm(Element element) throws PDFNetException {
 
+        try (var bbox = element.getBBox();) {
             return ElementFeatures.Form.builder()
                     .elementType(element.getType())
-                .boundingBox(Converter.toRectangle2D(element.getBBox()))
+                    .boundingBox(Converter.toRectangle2D(bbox))
                     .xObjectType(element.getXObject().getType())
                     .dictOrArrayOrStreamLength(element.getXObject().getType() == 7 ? element.getXObject().getDecodedStream().size() : 0)
                     .build();
         }
+    }
 
 
     private static ElementFeatures.Image.ImageBuilder<?, ?> buildImage(Element element) throws PDFNetException {
 
+        try (var bbox = element.getBBox();) {
             return ElementFeatures.Image.builder()
                     .elementType(element.getType())
-                .boundingBox(Converter.toRectangle2D(element.getBBox()))
+                    .boundingBox(Converter.toRectangle2D(bbox))
                     .dataSize(element.getImageDataSize())
                     .height(element.getImageHeight())
                     .width(element.getImageWidth())
@@ -46,35 +52,41 @@ public class ElementFeatureFactory {
                     .componentNum(element.getComponentNum())
                     .bitsPerComponent(element.getBitsPerComponent());
         }
+    }
 
 
     private static ElementFeatures.Text buildText(Element element) throws PDFNetException {
 
+        try (var bbox = element.getBBox();) {
             return ElementFeatures.Text.builder()
                     .elementType(element.getType())
-                .boundingBox(Converter.toRectangle2D(element.getBBox()))
+                    .boundingBox(Converter.toRectangle2D(bbox))
                     .text(element.getTextString())
                     .font(element.getGState().getFont().getType())
                     .fontsize(element.getGState().getFontSize())
                     .build();
         }
+    }
 
 
     private static ElementFeatures.Path buildPath(Element element) throws PDFNetException {
 
+        try (var bbox = element.getBBox(); var ctm = element.getCTM();
+             var fillColor = element.getGState().getFillColor();
+             var strokeColor = element.getGState().getStrokeColor()) {
             return ElementFeatures.Path.builder()
                     .elementType(element.getType())
-                .boundingBox(Converter.toRectangle2D(element.getBBox()))
+                    .boundingBox(Converter.toRectangle2D(bbox))
                     .isClippingPath(element.isClippingPath())
                     .isClipWindingFill(element.isClipWindingFill())
                     .isStroked(element.isStroked())
                     .isFilled(element.isFilled())
                     .isWindingFill(element.isWindingFill())
-                .fillColor(Converter.convertColor(element.getGState().getFillColorSpace(), element.getGState().getFillColor()))
+                    .fillColor(Converter.convertColor(element.getGState().getFillColorSpace(), fillColor))
-                .strokeColor(Converter.convertColor(element.getGState().getStrokeColorSpace(), element.getGState().getStrokeColor()))
+                    .strokeColor(Converter.convertColor(element.getGState().getStrokeColorSpace(), strokeColor))
-                .linePath(Converter.convertToGeneralPathAndTransformToInitialUserSpace(element.getPathData(), element.getCTM()))
+                    .linePath(Converter.convertToGeneralPathAndTransformToInitialUserSpace(element.getPathData(), ctm))
                     .build();
         }
-
+    }
 
 }

src/main/java/com/iqser/red/pdftronlogic/commons/ElementFeatures.java

@@ -31,9 +31,11 @@ public class ElementFeatures {
 
     public boolean almostMatches(Element element) throws PDFNetException {
 
+        try (var bbox = element.getBBox()) {
             return element.getType() == elementType && //
-                element.getBBox() != null && //
+                   bbox != null && //
-                rectsAlmostMatch(element.getBBox());
+                   rectsAlmostMatch(bbox);
+        }
     }
 
 
@@ -199,7 +201,10 @@ public class ElementFeatures {
             if (elementFeatures.getClass() != this.getClass()) {
                 return false;
             }
-            return super.almostMatches(elementFeatures) && this.dataSize == ((Image) elementFeatures).getDataSize() && this.height == ((Image) elementFeatures).getHeight() && this.width == ((Image) elementFeatures).getWidth() && this.renderingIntent == ((Image) elementFeatures).getRenderingIntent() && this.componentNum == ((Image) elementFeatures).getComponentNum() && this.bitsPerComponent == ((Image) elementFeatures).getBitsPerComponent() && calculateHammingDistance(
+            return super.almostMatches(elementFeatures) && this.dataSize == ((Image) elementFeatures).getDataSize() && this.height == ((Image) elementFeatures).getHeight() &&
+                   this.width == ((Image) elementFeatures).getWidth() && this.renderingIntent == ((Image) elementFeatures).getRenderingIntent() &&
+                   this.componentNum == ((Image) elementFeatures).getComponentNum() && this.bitsPerComponent == ((Image) elementFeatures).getBitsPerComponent() &&
+                   calculateHammingDistance(
                            ((Image) elementFeatures).getHashOfImage()) <= HAMMING_DISTANCE_THRESHOLD;
         }
 
@@ -241,11 +246,13 @@ public class ElementFeatures {
         @Override
         public boolean almostMatches(Element element) throws PDFNetException {
 
+            try (var bbox = element.getBBox()) {
                 return element.getType() == getElementType() && //
-                    element.getBBox() != null && //
+                       bbox != null && //
-                    (super.rectsAlmostMatch(element.getBBox()) || almostRotateMatches(element.getBBox().getRectangle())) && xObjectType == element.getXObject()
+                       (super.rectsAlmostMatch(bbox) || almostRotateMatches(bbox.getRectangle())) && xObjectType == element.getXObject()
                         .getType() && dictOrArrayOrStreamLength == element.getXObject().getDecodedStream().size();
             }
+        }
 
 
         public boolean almostMatches(ElementFeatures elementFeatures) {
@@ -253,9 +260,11 @@ public class ElementFeatures {
             if (elementFeatures.getClass() != this.getClass()) {
                 return false;
             }
-            return elementFeatures.getElementType() == getElementType() && elementFeatures.getBoundingBox() != null && (super.rectsAlmostMatch(elementFeatures.getBoundingBox()) || almostRotateMatches(
+            return elementFeatures.getElementType() == getElementType() && elementFeatures.getBoundingBox() != null &&
+                   (super.rectsAlmostMatch(elementFeatures.getBoundingBox()) || almostRotateMatches(
                            elementFeatures.getBoundingBox()
-                            .getBounds2D())) && xObjectType == ((Form) elementFeatures).getXObjectType() && dictOrArrayOrStreamLength == ((Form) elementFeatures).getDictOrArrayOrStreamLength();
+                                   .getBounds2D())) && xObjectType == ((Form) elementFeatures).getXObjectType() &&
+                   dictOrArrayOrStreamLength == ((Form) elementFeatures).getDictOrArrayOrStreamLength();
 
         }
 

src/main/java/com/iqser/red/pdftronlogic/commons/InvisibleElementRemovalService.java

@@ -63,15 +63,12 @@ public class InvisibleElementRemovalService {
 
         PDFDoc pdfDoc = new PDFDoc(pdfFile);
 
+        try (pdfDoc) {
             execute(pdfDoc, delta, removePaths, markedContentToIgnore);
-
-        try {
             pdfDoc.save(out, SDFDoc.SaveMode.LINEARIZED, null);
         } catch (Exception e) {
             log.error("File could not be saved after invisible element removal");
             throw new RuntimeException(e);
-        } finally {
-            pdfDoc.close();
         }
 
     }
@@ -151,7 +148,7 @@ public class InvisibleElementRemovalService {
     private void execute(PDFDoc pdfDoc, boolean delta, boolean removePaths, Set<String> markedContentToIgnore) {
 
         log.info("Start removing invisible Elements");
-        try(ElementWriter writer = new ElementWriter();
+        try (ElementWriter writer = new ElementWriter();
              ElementReader reader = new ElementReader()) {
             Set<Long> visitedXObjIds = new TreeSet<>();
 
@@ -236,7 +233,7 @@ public class InvisibleElementRemovalService {
 
     private void processImages(Element imageElement, ElementWriter writer, InvisibleElementRemovalContext context) throws PDFNetException {
 
-        try(Rect rect = imageElement.getBBox()) {
+        try (Rect rect = imageElement.getBBox()) {
 
             if (rect == null) {
                 return;
@@ -257,7 +254,7 @@ public class InvisibleElementRemovalService {
 
     private void processText(Element textElement, ElementWriter writer, InvisibleElementRemovalContext context) throws PDFNetException {
 
-        try(Rect textBBox = textElement.getBBox()) {
+        try (Rect textBBox = textElement.getBBox()) {
 
             if (textBBox == null) {
                 writer.writeElement(textElement);
@@ -289,13 +286,17 @@ public class InvisibleElementRemovalService {
                 if (!inClippingPath) {
                     gState.setFillColorSpace(ColorSpace.createDeviceRGB());
                     // red for elements removed by clipping path
-                    gState.setFillColor(new ColorPt(1, 0, 0));
+                    try (var color = new ColorPt(1, 0, 0)) {
+                        gState.setFillColor(color);
+                    }
                     writer.writeElement(textElement);
                 }
                 if (!isTextVisible) {
                     gState.setFillColorSpace(ColorSpace.createDeviceRGB());
                     // blue for elements removed due to transparency or not rendered or same color as background
-                    gState.setFillColor(new ColorPt(0, 0, 1));
+                    try (var color = new ColorPt(0, 0, 1)) {
+                        gState.setFillColor(color);
+                    }
                     gState.setTextRenderMode(GState.e_fill_text);
                     gState.setFillOpacity(1);
                     writer.writeElement(textElement);
@@ -314,9 +315,10 @@ public class InvisibleElementRemovalService {
             context.visitedXObjIds().add(formObj.getObjNum());
             // writer needs to be newly initialized when entering a new content stream
             // see ElementEditTest in PDFTron (https://www.pdftron.com/documentation/samples/android/java/ElementEditTest)
-            try(ElementWriter formWriter = new ElementWriter()) {
+            try (ElementWriter formWriter = new ElementWriter()) {
                 context.clippingPathStack().enterNewGState();
-                context.clippingPathStack().intersectClippingPath(new GeneralPath(Converter.toRectangle2D(formElement.getBBox())));
+                try (var formElementBBOX = formElement.getBBox()) {
+                    context.clippingPathStack().intersectClippingPath(Converter.toRectangle2D(formElementBBOX));
                     context.reader().formBegin();
                     formWriter.begin(formObj);
 
@@ -330,18 +332,21 @@ public class InvisibleElementRemovalService {
                 }
             }
         }
+    }
 
 
     private void processPath(Element pathElement, ElementWriter writer, InvisibleElementRemovalContext context) throws PDFNetException {
 
         PathData pathData = pathElement.getPathData();
 
-        if (pathData.getOperators().length == 0 && pathData.getPoints().length == 0 || pathElement.getBBox() == null) {
+        try (var bbox = pathElement.getBBox()) {
+            if (pathData.getOperators().length == 0 && pathData.getPoints().length == 0 || bbox == null) {
                 writer.writeElement(pathElement);
                 return;
             }
 
-        GeneralPath linePath = Converter.convertToGeneralPathAndTransformToInitialUserSpace(pathData, pathElement.getCTM());
+            try (var ctm = pathElement.getCTM()) {
+                GeneralPath linePath = Converter.convertToGeneralPathAndTransformToInitialUserSpace(pathData, ctm);
 
                 var rect = linePath.getBounds2D();
 
@@ -377,14 +382,18 @@ public class InvisibleElementRemovalService {
                     }
 
                     if (context.delta() && !inClippingPath && context.removePaths()) {
+                        try (var color = new ColorPt(1, 0, 0)) {
                             pathElement.getGState().setFillColorSpace(ColorSpace.createDeviceRGB());
-                pathElement.getGState().setFillColor(new ColorPt(1, 0, 0));
+                            pathElement.getGState().setFillColor(color);
                             pathElement.getGState().setStrokeColorSpace(ColorSpace.createDeviceRGB());
-                pathElement.getGState().setStrokeColor(new ColorPt(1, 0, 0));
+                            pathElement.getGState().setStrokeColor(color);
                             writer.writeElement(pathElement);
                         }
                     }
                 }
+            }
+        }
+    }
 
 
     private void calculateOverlapsForLinePath(InvisibleElementRemovalContext context, GeneralPath linePath) {
@@ -480,7 +489,7 @@ public class InvisibleElementRemovalService {
             context.visitedXObjIds().add(formObj.getObjNum());
             // writer needs to be newly initialized when entering a new content stream
             // see ElementEditTest in PDFTron (https://www.pdftron.com/documentation/samples/android/java/ElementEditTest)
-            try(ElementWriter formWriter = new ElementWriter()) {
+            try (ElementWriter formWriter = new ElementWriter()) {
                 context.reader().formBegin();
                 formWriter.begin(formObj);
 
@@ -516,7 +525,9 @@ public class InvisibleElementRemovalService {
 
     private boolean fillIsVisible(GState gState, Rect textBBox, InvisibleElementRemovalContext context) throws PDFNetException {
 
-        return gState.getFillOpacity() != 0 && differentColorThanBackgroundColor(Converter.convertColor(gState.getFillColorSpace(), gState.getFillColor()), textBBox, context);
+        try (var color = gState.getFillColor()) {
+            return gState.getFillOpacity() != 0 && differentColorThanBackgroundColor(Converter.convertColor(gState.getFillColorSpace(), color), textBBox, context);
+        }
     }
 
 
@@ -541,13 +552,16 @@ public class InvisibleElementRemovalService {
 
     private static List<ElementFeatures.Path> findVisiblePathElementsThatIntersect(Rect textBBox, InvisibleElementRemovalContext context) {
 
-        return context.visibleElements()
+        var result = new ArrayList<ElementFeatures.Path>();
-                .stream()
+        for (var element : context.visibleElements()) {
-                .filter(elementFeatures -> elementFeatures.getElementType() == Element.e_path)
+            if (element.getElementType() == Element.e_path
-                .map(elementFeatures -> (ElementFeatures.Path) elementFeatures)
+                && !((ElementFeatures.Path) element).getFillColor().equals(Color.WHITE)
-                .filter(elementFeatures -> !elementFeatures.getFillColor().equals(Color.WHITE))
+                && ((ElementFeatures.Path) element).isBackground(textBBox)) {
-                .filter(element -> element.isBackground(textBBox))
+                result.add((ElementFeatures.Path) element);
-                .toList();
+            }
+        }
+        return result;
+
     }
 
 
@@ -581,7 +595,7 @@ public class InvisibleElementRemovalService {
     @SneakyThrows
     private void drawBBox(ElementWriter writer, Rectangle2D r, String hexcolor) {
 
-        try(ColorPt colorPt = new ColorPt(Integer.valueOf(hexcolor.substring(1, 3), 16) / 255d,
+        try (ColorPt colorPt = new ColorPt(Integer.valueOf(hexcolor.substring(1, 3), 16) / 255d,
                 Integer.valueOf(hexcolor.substring(3, 5), 16) / 255d,
                 Integer.valueOf(hexcolor.substring(5, 7), 16) / 255d);
              ElementBuilder eb = new ElementBuilder()) {

src/main/java/com/iqser/red/pdftronlogic/commons/WatermarkRemovalService.java

@@ -93,7 +93,7 @@ public class WatermarkRemovalService {
         Map<Long, List<ElementFeatures>> formObjectsAndImagesForPages = new HashMap<>();
         Set<Long> visitedXObjIds = new TreeSet<>();
 
-        try(ElementReader reader = new ElementReader()) {
+        try (ElementReader reader = new ElementReader()) {
 
             for (PageIterator iterator = pdfDoc.getPageIterator(); iterator.hasNext(); ) {
 
@@ -123,7 +123,8 @@ public class WatermarkRemovalService {
                                 double minAreaCoveringPage,
                                 Page page) throws PDFNetException {
 
-        if (element.getBBox() == null) {
+        try (var bbox = element.getBBox()) {
+            if (bbox == null) {
                 return;
             }
 
@@ -132,6 +133,7 @@ public class WatermarkRemovalService {
                 case Element.e_image, Element.e_inline_image -> processImages(element, elementFeaturesLinkedList, page, minAreaCoveringPage);
                 case Element.e_text -> processText(element, elementFeaturesLinkedList, page);
             }
+        }
 
     }
 
@@ -147,12 +149,14 @@ public class WatermarkRemovalService {
             return;
         }
 
-        boolean isBigEnough = Math.abs(element.getBBox().getY1() - element.getBBox().getY2()) > page.getPageHeight() * MIN_TEXTWATERMARK_HEIGHT_THRESHOLD;
+        try (var bbox = element.getBBox()) {
+            boolean isBigEnough = Math.abs(bbox.getY1() - bbox.getY2()) > page.getPageHeight() * MIN_TEXTWATERMARK_HEIGHT_THRESHOLD;
 
             if (isBigEnough) {
                 ElementFeatures elementFeatures = ElementFeatureFactory.extractFeatures(element);
                 elementFeaturesLinkedList.add(elementFeatures);
             }
+        }
 
     }
 
@@ -160,9 +164,11 @@ public class WatermarkRemovalService {
     @SneakyThrows
     private boolean isTextRotated(Element element) {
 
-        return Math.abs(element.getCTM().getB()) < Math.sin(Math.toRadians(ROTATED_TEXT_THRESHOLD)) || Math.abs(element.getCTM()
+        try (var ctm = element.getCTM()) {
+            return Math.abs(ctm.getB()) < Math.sin(Math.toRadians(ROTATED_TEXT_THRESHOLD)) || Math.abs(ctm
                     .getB()) > Math.sin(Math.toRadians(70 - ROTATED_TEXT_THRESHOLD));
         }
+    }
 
 
     private void shouldTextSearchBeContinued(List<ElementFeatures> elementFeaturesLinkedList) {
@@ -185,7 +191,8 @@ public class WatermarkRemovalService {
         if (element.getXObject() == null) {
             return;
         }
-        if (element.getBBox().getHeight() * element.getBBox().getWidth() < minAreaCoveringPage && isLocatedNearBorder(element, page)) {
+        try (var bbox = element.getBBox()) {
+            if (bbox.getHeight() * bbox.getWidth() < minAreaCoveringPage && isLocatedNearBorder(element, page)) {
                 return;
             }
 
@@ -193,16 +200,25 @@ public class WatermarkRemovalService {
             ElementFeatures elementFeatures = ElementFeatureFactory.extractFeaturesWithHash(element, hashOfImage);
             elementFeaturesLinkedList.add(elementFeatures);
         }
+    }
 
 
     // Typically company logos on dossier pages are located near the border and should be excluded from the watermark removal
     @SneakyThrows
     private boolean isLocatedNearBorder(Element element, Page page) {
 
-        return element.getBBox().getY1() < page.getVisibleContentBox().getY1() + page.getPageHeight() * IMAGE_POSITION_HEIGHT_THRESHOLD || element.getBBox()
+        try (var bbox = element.getBBox(); var contentBox = page.getVisibleContentBox();) {
-                .getY2() > page.getVisibleContentBox().getY2() - page.getPageHeight() * IMAGE_POSITION_HEIGHT_THRESHOLD || element.getBBox().getX1() < page.getVisibleContentBox()
+            return bbox.getY1() < contentBox.getY1() + page.getPageHeight() * IMAGE_POSITION_HEIGHT_THRESHOLD || bbox
-                .getX1() + page.getPageWidth() * IMAGE_POSITION_WIDTH_THRESHOLD || element.getBBox().getX2() > page.getVisibleContentBox()
+                                                                                                                         .getY2() >
-                .getX2() - page.getPageWidth() * IMAGE_POSITION_WIDTH_THRESHOLD;
+                                                                                                                 contentBox.getY2() -
+                                                                                                                 page.getPageHeight() *
+                                                                                                                 IMAGE_POSITION_HEIGHT_THRESHOLD ||
+                   bbox.getX1() < contentBox
+                                          .getX1() + page.getPageWidth() * IMAGE_POSITION_WIDTH_THRESHOLD || bbox.getX2() > contentBox
+                                                                                                                                    .getX2() -
+                                                                                                                            page.getPageWidth() *
+                                                                                                                            IMAGE_POSITION_WIDTH_THRESHOLD;
+        }
     }
 
 
@@ -214,12 +230,14 @@ public class WatermarkRemovalService {
                                 double minAreaCoveringPage,
                                 Page page) {
 
-        if (element.getBBox().getHeight() * element.getBBox().getWidth() < minAreaCoveringPage) {
+        try (var bbox = element.getBBox()) {
+            if (bbox.getHeight() * bbox.getWidth() < minAreaCoveringPage) {
                 return;
             }
+        }
 
         if (visitedXObjIds.add(element.getXObject().getObjNum())) {
-            try(ElementReader xObjectReader = new ElementReader()) {
+            try (ElementReader xObjectReader = new ElementReader()) {
                 xObjectReader.begin(element.getXObject());
                 for (Element element1 = xObjectReader.next(); element1 != null; element1 = xObjectReader.next()) {
                     processElement(element1, visitedXObjIds, elementFeaturesLinkedList, formObjectsOccuringMoreThanOnceOnAPage, minAreaCoveringPage, page);
@@ -246,7 +264,9 @@ public class WatermarkRemovalService {
                 .filter(elementFeature -> formObjectsPerPage.values()
                                                   .stream()
                                                   .filter(elementFeaturesOnPage -> elementFeaturesOnPage.stream()
-                                .anyMatch(elementFeature.getElementType() == Element.e_image || elementFeature.getElementType() == Element.e_inline_image ? elementFeature::isSimilarTo : elementFeature::almostMatches))
+                                                          .anyMatch(
+                                                                  elementFeature.getElementType() == Element.e_image || elementFeature.getElementType() == Element.e_inline_image ?
+                                                                  elementFeature::isSimilarTo : elementFeature::almostMatches))
                                                   .count() >= minPagesFilter)
                 .toList();
     }
@@ -255,7 +275,7 @@ public class WatermarkRemovalService {
     @SneakyThrows
     private void removeAllWatermarks(PDFDoc pdfDoc, List<ElementFeatures> watermarksElementFeaturesList) {
 
-        try(ElementReader reader = new ElementReader();
+        try (ElementReader reader = new ElementReader();
              ElementWriter writer = new ElementWriter()) {
             Set<Long> visitedXObjIds = new TreeSet<>();
 
@@ -295,17 +315,25 @@ public class WatermarkRemovalService {
 
             switch (element.getType()) {
                 case Element.e_image, Element.e_inline_image -> {
-                    if (element.getBBox() == null) {
+                    try (var bbox = element.getBBox()) {
+                        if (bbox == null) {
                             writer.writeElement(element);
                             continue;
                         }
-                    if (element.getBBox().getHeight() * element.getBBox().getWidth() < minAreaCoveringFromPage && isLocatedNearBorder(element, page) && element.getBBox()
+                    }
-                            .getHeight() * element.getBBox().getWidth() < minAreaCoveringFromPage || element.getXObject() == null) {
+                    try (var bbox = element.getBBox()) {
+                        if (bbox.getHeight() * bbox.getWidth() < minAreaCoveringFromPage && isLocatedNearBorder(element, page) && bbox
+                                                                                                                                          .getHeight() *
+                                                                                                                                  bbox
+                                                                                                                                          .getWidth() <
+                                                                                                                                  minAreaCoveringFromPage ||
+                            element.getXObject() == null) {
 
                             writer.writeElement(element);
                             continue;
 
                         }
+                    }
                     removeImages(element, writer, watermarksElementFeaturesList);
                 }
                 case Element.e_form -> processForms(page, element, reader, writer, watermarksElementFeaturesList, visitedXObjIds);
@@ -344,9 +372,11 @@ public class WatermarkRemovalService {
             return false;
         }
 
-        if (Math.max(element.getBBox().getY1(), element.getBBox().getY2()) < page.getVisibleContentBox().getY1() + page.getPageHeight() * TEXT_POSITION_THRESHOLD) {
+        try (var bbox = element.getBBox(); var contents = page.getVisibleContentBox();) {
+            if (Math.max(bbox.getY1(), bbox.getY2()) < contents.getY1() + page.getPageHeight() * TEXT_POSITION_THRESHOLD) {
                 return false;
             }
+        }
         return true;
     }
 
@@ -385,7 +415,7 @@ public class WatermarkRemovalService {
             visitedXObjIds.add(element.getXObject().getObjNum());
             // writer needs to be newly initialized when entering a new content stream
             // see ElementEditTest in PDFTron (https://www.pdftron.com/documentation/samples/android/java/ElementEditTest)
-            try(ElementWriter formWriter = new ElementWriter()) {
+            try (ElementWriter formWriter = new ElementWriter()) {
                 reader.formBegin();
                 formWriter.begin(element.getXObject());
 

src/test/java/com/iqser/red/pdftronlogic/commons/InvisibleElementRemovalServiceTest.java

@@ -6,6 +6,7 @@ import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 
+import lombok.extern.slf4j.Slf4j;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
@@ -14,6 +15,7 @@ import com.pdftron.pdf.PDFNet;
 import lombok.SneakyThrows;
 
 @SuppressWarnings("PMD")
+@Slf4j
 class InvisibleElementRemovalServiceTest {
 
     InvisibleElementRemovalService invisibleElementRemovalService;
@@ -101,8 +103,19 @@ class InvisibleElementRemovalServiceTest {
             String result = PdfTextExtraction.extractAllTextFromDocument(in);
             assertThat(result).contains("#1 Dark",
                     "#13 Yellow",
-                    "Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip\n" + "ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie\n" + "consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim\n" + "qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi.");
+                    "Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip\n" +
-            assertThat(result).doesNotContain("Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut\n" + "labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et\n" + "ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem\n" + "ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et\n" + "dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea\n" + "rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum\n" + "dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore\n" + "magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet\n" + "clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. ");
+                    "ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie\n" +
+                    "consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim\n" +
+                    "qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi.");
+            assertThat(result).doesNotContain("Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut\n" +
+                                              "labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et\n" +
+                                              "ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem\n" +
+                                              "ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et\n" +
+                                              "dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea\n" +
+                                              "rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum\n" +
+                                              "dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore\n" +
+                                              "magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet\n" +
+                                              "clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. ");
         }
 
     }