feat(cbr-to-pdf,pdf-to-cbr): add PDF to/from CBR conversion with ebook optimization option (#4581)

# Description of Changes

This pull request adds support for converting CBR (Comic Book RAR) files
to PDF, optimizes CBZ/CBR-to-PDF conversion for e-readers using
Ghostscript, and improves file type detection and image file handling.
It introduces the `CbrUtils` and `PdfToCbrUtils` utility classes,
refactors CBZ conversion logic, and integrates these features into the
API controller. The most important changes are grouped below.

### CBR Support and Conversion:

- Added the `com.github.junrar:junrar` dependency to support RAR/CBR
archive extraction in `build.gradle`. (https://github.com/junrar/junrar
and https://github.com/junrar/junrar?tab=License-1-ov-file#readme for
repo and license)
- Introduced the new utility class `CbrUtils` for converting CBR files
to PDF, including image extraction, sorting, and error handling.
- Added the `PdfToCbrUtils` utility class to convert PDF files into CBR
archives by rendering each page as an image and packaging them.

### CBZ/CBR Conversion Optimization:

- Refactored `CbzUtils.convertCbzToPdf` to support optional Ghostscript
optimization for e-reader compatibility and added a new method for this.
- Added `GeneralUtils.optimizePdfWithGhostscript`, which uses
Ghostscript to optimize PDFs for e-readers, and integrated error
handling.

### API Controller Integration:

- Updated `ConvertImgPDFController` to support CBR conversion, CBZ/CBR
optimization toggling, and Ghostscript availability checks.

### Endpoints
<img width="1298" height="522" alt="image"
src="https://github.com/user-attachments/assets/144d3e03-a637-451a-9c35-f784b2a66dc1"
/>

<img width="1279" height="472" alt="image"
src="https://github.com/user-attachments/assets/879f221d-b775-4224-8edb-a23dbea6a0ca"
/>

### UI

<img width="384" height="105" alt="image"
src="https://github.com/user-attachments/assets/5f861943-0706-4fad-8775-c40a9c1f3170"
/>


### File Type and Image Detection Improvements:

- Improved file extension detection for comic book files and image files
in `CbzUtils` and added a shared regex pattern utility for image files.

### Additional notes:
- Please keep in mind new the dependency, this is not dependency-free
implementation (as opposed to CBZ converter)
- RAR 5 currently not supported. (because JUNRAR does not support it)
- Added the new ebook optimization func to GeneralUtils since we'll soon
(hopefully) at least 3 book/ebook formats (EPUB, CBZ, CBR) all of which
can use it.
- Once again this has been thoroughly tested but can't share actual
"real life" file due to copyright.


Closes: #775
<!--
Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)
-->

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [x] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [x] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Signed-off-by: Balázs Szücs <bszucs1209@gmail.com>

app/allowed-licenses.json

@@ -167,6 +167,10 @@
     {
       "moduleName": ".*",
       "moduleLicense": "The W3C License"
+    },
+    {
+      "moduleName": ".*",
+      "moduleLicense": "UnRar License"
     }
   ]
 }

app/common/build.gradle

@@ -37,6 +37,7 @@ dependencies {
     api 'com.drewnoakes:metadata-extractor:2.19.0' // Image metadata extractor
     api 'com.vladsch.flexmark:flexmark-html2md-converter:0.64.8'
     api "org.apache.pdfbox:pdfbox:$pdfboxVersion"
+    api 'com.github.junrar:junrar:7.5.5' // RAR archive support for CBR files
     api 'jakarta.servlet:jakarta.servlet-api:6.1.0'
     api 'org.snakeyaml:snakeyaml-engine:2.10'
     api "org.springdoc:springdoc-openapi-starter-webmvc-ui:2.8.13"

app/common/src/main/java/stirling/software/common/util/CbrUtils.java

@@ -0,0 +1,258 @@
+package stirling.software.common.util;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+
+import org.apache.commons.io.FilenameUtils;
+import org.apache.pdfbox.pdmodel.PDDocument;
+import org.apache.pdfbox.pdmodel.PDPage;
+import org.apache.pdfbox.pdmodel.PDPageContentStream;
+import org.apache.pdfbox.pdmodel.common.PDRectangle;
+import org.apache.pdfbox.pdmodel.graphics.image.PDImageXObject;
+import org.springframework.web.multipart.MultipartFile;
+
+import com.github.junrar.Archive;
+import com.github.junrar.exception.CorruptHeaderException;
+import com.github.junrar.exception.RarException;
+import com.github.junrar.rarfile.FileHeader;
+
+import lombok.experimental.UtilityClass;
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.common.service.CustomPDFDocumentFactory;
+
+@Slf4j
+@UtilityClass
+public class CbrUtils {
+
+    public byte[] convertCbrToPdf(
+            MultipartFile cbrFile,
+            CustomPDFDocumentFactory pdfDocumentFactory,
+            TempFileManager tempFileManager)
+            throws IOException {
+        return convertCbrToPdf(cbrFile, pdfDocumentFactory, tempFileManager, false);
+    }
+
+    public byte[] convertCbrToPdf(
+            MultipartFile cbrFile,
+            CustomPDFDocumentFactory pdfDocumentFactory,
+            TempFileManager tempFileManager,
+            boolean optimizeForEbook)
+            throws IOException {
+
+        validateCbrFile(cbrFile);
+
+        try (TempFile tempFile = new TempFile(tempFileManager, ".cbr")) {
+            cbrFile.transferTo(tempFile.getFile());
+
+            try (PDDocument document = pdfDocumentFactory.createNewDocument()) {
+
+                Archive archive;
+                try {
+                    archive = new Archive(tempFile.getFile());
+                } catch (CorruptHeaderException e) {
+                    log.warn(
+                            "Failed to open CBR/RAR archive due to corrupt header: {}",
+                            e.getMessage());
+                    throw ExceptionUtils.createIllegalArgumentException(
+                            "error.invalidFormat",
+                            "Invalid or corrupted CBR/RAR archive. "
+                                    + "The file may be corrupted, use an unsupported RAR format (RAR5+), "
+                                    + "or may not be a valid RAR archive. "
+                                    + "Please ensure the file is a valid RAR archive.");
+                } catch (RarException e) {
+                    log.warn("Failed to open CBR/RAR archive: {}", e.getMessage());
+                    String errorMessage;
+                    String exMessage = e.getMessage() != null ? e.getMessage() : "";
+
+                    if (exMessage.contains("encrypted")) {
+                        errorMessage = "Encrypted CBR/RAR archives are not supported.";
+                    } else if (exMessage.isEmpty()) {
+                        errorMessage =
+                                "Invalid CBR/RAR archive. "
+                                        + "The file may be encrypted, corrupted, or use an unsupported format.";
+                    } else {
+                        errorMessage =
+                                "Invalid CBR/RAR archive: "
+                                        + exMessage
+                                        + ". The file may be encrypted, corrupted, or use an unsupported format.";
+                    }
+                    throw ExceptionUtils.createIllegalArgumentException(
+                            "error.invalidFormat", errorMessage);
+                } catch (IOException e) {
+                    log.warn("IO error reading CBR/RAR archive: {}", e.getMessage());
+                    throw ExceptionUtils.createFileProcessingException("CBR extraction", e);
+                }
+
+                List<ImageEntryData> imageEntries = new ArrayList<>();
+
+                try {
+                    for (FileHeader fileHeader : archive) {
+                        if (!fileHeader.isDirectory() && isImageFile(fileHeader.getFileName())) {
+                            try (InputStream is = archive.getInputStream(fileHeader)) {
+                                ByteArrayOutputStream baos = new ByteArrayOutputStream();
+                                is.transferTo(baos);
+                                imageEntries.add(
+                                        new ImageEntryData(
+                                                fileHeader.getFileName(), baos.toByteArray()));
+                            } catch (Exception e) {
+                                log.warn(
+                                        "Error reading image {}: {}",
+                                        fileHeader.getFileName(),
+                                        e.getMessage());
+                            }
+                        }
+                    }
+                } finally {
+                    try {
+                        archive.close();
+                    } catch (IOException e) {
+                        log.warn("Error closing CBR/RAR archive: {}", e.getMessage());
+                    }
+                }
+
+                imageEntries.sort(
+                        Comparator.comparing(ImageEntryData::name, new NaturalOrderComparator()));
+
+                if (imageEntries.isEmpty()) {
+                    throw ExceptionUtils.createIllegalArgumentException(
+                            "error.fileProcessing",
+                            "No valid images found in the CBR file. The archive may be empty or contain no supported image formats.");
+                }
+
+                for (ImageEntryData imageEntry : imageEntries) {
+                    try {
+                        PDImageXObject pdImage =
+                                PDImageXObject.createFromByteArray(
+                                        document, imageEntry.data(), imageEntry.name());
+                        PDPage page =
+                                new PDPage(
+                                        new PDRectangle(pdImage.getWidth(), pdImage.getHeight()));
+                        document.addPage(page);
+                        try (PDPageContentStream contentStream =
+                                new PDPageContentStream(document, page)) {
+                            contentStream.drawImage(pdImage, 0, 0);
+                        }
+                    } catch (IOException e) {
+                        log.warn(
+                                "Error processing image {}: {}", imageEntry.name(), e.getMessage());
+                    }
+                }
+
+                if (document.getNumberOfPages() == 0) {
+                    throw ExceptionUtils.createIllegalArgumentException(
+                            "error.fileProcessing",
+                            "No images could be processed from the CBR file. All images may be corrupted or in unsupported formats.");
+                }
+
+                ByteArrayOutputStream baos = new ByteArrayOutputStream();
+                document.save(baos);
+                byte[] pdfBytes = baos.toByteArray();
+
+                // Apply Ghostscript optimization if requested
+                if (optimizeForEbook) {
+                    try {
+                        return GeneralUtils.optimizePdfWithGhostscript(pdfBytes);
+                    } catch (IOException e) {
+                        log.warn("Ghostscript optimization failed, returning unoptimized PDF", e);
+                        return pdfBytes;
+                    }
+                }
+
+                return pdfBytes;
+            }
+        }
+    }
+
+    private void validateCbrFile(MultipartFile file) {
+        if (file == null || file.isEmpty()) {
+            throw new IllegalArgumentException("File cannot be null or empty");
+        }
+
+        String filename = file.getOriginalFilename();
+        if (filename == null) {
+            throw new IllegalArgumentException("File must have a name");
+        }
+
+        String extension = FilenameUtils.getExtension(filename).toLowerCase();
+        if (!"cbr".equals(extension) && !"rar".equals(extension)) {
+            throw new IllegalArgumentException("File must be a CBR or RAR archive");
+        }
+    }
+
+    public boolean isCbrFile(MultipartFile file) {
+        String filename = file.getOriginalFilename();
+        if (filename == null) {
+            return false;
+        }
+
+        String extension = FilenameUtils.getExtension(filename).toLowerCase();
+        return "cbr".equals(extension) || "rar".equals(extension);
+    }
+
+    private boolean isImageFile(String filename) {
+        return RegexPatternUtils.getInstance().getImageFilePattern().matcher(filename).matches();
+    }
+
+    private record ImageEntryData(String name, byte[] data) {}
+
+    private class NaturalOrderComparator implements Comparator<String> {
+        private static String getChunk(String s, int length, int marker) {
+            StringBuilder chunk = new StringBuilder();
+            char c = s.charAt(marker);
+            chunk.append(c);
+            marker++;
+
+            if (isDigit(c)) {
+                while (marker < length && isDigit(s.charAt(marker))) {
+                    chunk.append(s.charAt(marker));
+                    marker++;
+                }
+            } else {
+                while (marker < length && !isDigit(s.charAt(marker))) {
+                    chunk.append(s.charAt(marker));
+                    marker++;
+                }
+            }
+            return chunk.toString();
+        }
+
+        private static boolean isDigit(char ch) {
+            return ch >= '0' && ch <= '9';
+        }
+
+        @Override
+        public int compare(String s1, String s2) {
+            int len1 = s1.length();
+            int len2 = s2.length();
+            int marker1 = 0, marker2 = 0;
+
+            while (marker1 < len1 && marker2 < len2) {
+                String chunk1 = getChunk(s1, len1, marker1);
+                marker1 += chunk1.length();
+
+                String chunk2 = getChunk(s2, len2, marker2);
+                marker2 += chunk2.length();
+
+                int result;
+                if (isDigit(chunk1.charAt(0)) && isDigit(chunk2.charAt(0))) {
+                    int thisNumericValue = Integer.parseInt(chunk1);
+                    int thatNumericValue = Integer.parseInt(chunk2);
+                    result = Integer.compare(thisNumericValue, thatNumericValue);
+                } else {
+                    result = chunk1.compareTo(chunk2);
+                }
+
+                if (result != 0) {
+                    return result;
+                }
+            }
+
+            return Integer.compare(len1, len2);
+        }
+    }
+}

app/common/src/main/java/stirling/software/common/util/CbzUtils.java

@@ -8,7 +8,6 @@ import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.Enumeration;
 import java.util.List;
-import java.util.regex.Pattern;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
 import java.util.zip.ZipInputStream;
@@ -30,14 +29,20 @@ import stirling.software.common.service.CustomPDFDocumentFactory;
 @UtilityClass
 public class CbzUtils {
 
-    private final Pattern IMAGE_PATTERN =
-            Pattern.compile(".*\\.(jpg|jpeg|png|gif|bmp|webp)$", Pattern.CASE_INSENSITIVE);
-
     public byte[] convertCbzToPdf(
             MultipartFile cbzFile,
             CustomPDFDocumentFactory pdfDocumentFactory,
             TempFileManager tempFileManager)
             throws IOException {
+        return convertCbzToPdf(cbzFile, pdfDocumentFactory, tempFileManager, false);
+    }
+
+    public byte[] convertCbzToPdf(
+            MultipartFile cbzFile,
+            CustomPDFDocumentFactory pdfDocumentFactory,
+            TempFileManager tempFileManager,
+            boolean optimizeForEbook)
+            throws IOException {
 
         validateCbzFile(cbzFile);
 
@@ -106,7 +111,19 @@ public class CbzUtils {
                 }
                 ByteArrayOutputStream baos = new ByteArrayOutputStream();
                 document.save(baos);
-                return baos.toByteArray();
+                byte[] pdfBytes = baos.toByteArray();
+
+                // Apply Ghostscript optimization if requested
+                if (optimizeForEbook) {
+                    try {
+                        return GeneralUtils.optimizePdfWithGhostscript(pdfBytes);
+                    } catch (IOException e) {
+                        log.warn("Ghostscript optimization failed, returning unoptimized PDF", e);
+                        return pdfBytes;
+                    }
+                }
+
+                return pdfBytes;
             }
         }
     }
@@ -137,8 +154,21 @@ public class CbzUtils {
         return "cbz".equals(extension) || "zip".equals(extension);
     }
 
+    public static boolean isComicBookFile(MultipartFile file) {
+        String filename = file.getOriginalFilename();
+        if (filename == null) {
+            return false;
+        }
+
+        String extension = FilenameUtils.getExtension(filename).toLowerCase();
+        return "cbz".equals(extension)
+                || "zip".equals(extension)
+                || "cbr".equals(extension)
+                || "rar".equals(extension);
+    }
+
     private boolean isImageFile(String filename) {
-        return IMAGE_PATTERN.matcher(filename).matches();
+        return RegexPatternUtils.getInstance().getImageFilePattern().matcher(filename).matches();
     }
 
     private record ImageEntryData(String name, byte[] data) {}

app/common/src/main/java/stirling/software/common/util/GeneralUtils.java

@@ -905,4 +905,67 @@ public class GeneralUtils {
         // If all components so far are equal, the longer version is considered higher
         return current.length > compare.length;
     }
+
+    /**
+     * Optimizes a PDF using Ghostscript with ebook settings for better e-reader compatibility. Uses
+     * -dPDFSETTINGS=/ebook -dFastWebView=true settings to create an optimized PDF.
+     *
+     * @param inputPdfBytes Original PDF as byte array
+     * @return Optimized PDF as byte array
+     * @throws IOException if Ghostscript optimization fails
+     */
+    public byte[] optimizePdfWithGhostscript(byte[] inputPdfBytes) throws IOException {
+        Path tempInput = null;
+        Path tempOutput = null;
+
+        try {
+            tempInput = Files.createTempFile("gs_input_", ".pdf");
+            tempOutput = Files.createTempFile("gs_output_", ".pdf");
+
+            Files.write(tempInput, inputPdfBytes);
+
+            List<String> command = new ArrayList<>();
+            command.add("gs");
+            command.add("-sDEVICE=pdfwrite");
+            command.add("-dPDFSETTINGS=/ebook");
+            command.add("-dFastWebView=true");
+            command.add("-dNOPAUSE");
+            command.add("-dQUIET");
+            command.add("-dBATCH");
+            command.add("-sOutputFile=" + tempOutput.toString());
+            command.add(tempInput.toString());
+
+            ProcessExecutor.ProcessExecutorResult result =
+                    ProcessExecutor.getInstance(ProcessExecutor.Processes.GHOSTSCRIPT)
+                            .runCommandWithOutputHandling(command);
+
+            if (result.getRc() != 0) {
+                log.warn(
+                        "Ghostscript ebook optimization failed with return code: {}",
+                        result.getRc());
+                throw ExceptionUtils.createGhostscriptCompressionException();
+            }
+
+            return Files.readAllBytes(tempOutput);
+
+        } catch (Exception e) {
+            log.warn("Ghostscript ebook optimization failed", e);
+            throw ExceptionUtils.createGhostscriptCompressionException(e);
+        } finally {
+            if (tempInput != null) {
+                try {
+                    Files.deleteIfExists(tempInput);
+                } catch (IOException e) {
+                    log.warn("Failed to delete temp input file: {}", tempInput, e);
+                }
+            }
+            if (tempOutput != null) {
+                try {
+                    Files.deleteIfExists(tempOutput);
+                } catch (IOException e) {
+                    log.warn("Failed to delete temp output file: {}", tempOutput, e);
+                }
+            }
+        }
+    }
 }

app/common/src/main/java/stirling/software/common/util/PdfToCbrUtils.java

@@ -0,0 +1,99 @@
+package stirling.software.common.util;
+
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipOutputStream;
+
+import javax.imageio.ImageIO;
+
+import org.apache.commons.io.FilenameUtils;
+import org.apache.pdfbox.pdmodel.PDDocument;
+import org.apache.pdfbox.rendering.ImageType;
+import org.apache.pdfbox.rendering.PDFRenderer;
+import org.springframework.web.multipart.MultipartFile;
+
+import lombok.extern.slf4j.Slf4j;
+
+import stirling.software.common.service.CustomPDFDocumentFactory;
+
+@Slf4j
+public class PdfToCbrUtils {
+
+    public static byte[] convertPdfToCbr(
+            MultipartFile pdfFile, int dpi, CustomPDFDocumentFactory pdfDocumentFactory)
+            throws IOException {
+
+        validatePdfFile(pdfFile);
+
+        try (PDDocument document = pdfDocumentFactory.load(pdfFile)) {
+            if (document.getNumberOfPages() == 0) {
+                throw new IllegalArgumentException("PDF file contains no pages");
+            }
+
+            return createCbrFromPdf(document, dpi);
+        }
+    }
+
+    private static void validatePdfFile(MultipartFile file) {
+        if (file == null || file.isEmpty()) {
+            throw new IllegalArgumentException("File cannot be null or empty");
+        }
+
+        String filename = file.getOriginalFilename();
+        if (filename == null) {
+            throw new IllegalArgumentException("File must have a name");
+        }
+
+        String extension = FilenameUtils.getExtension(filename).toLowerCase();
+        if (!"pdf".equals(extension)) {
+            throw new IllegalArgumentException("File must be a PDF");
+        }
+    }
+
+    private static byte[] createCbrFromPdf(PDDocument document, int dpi) throws IOException {
+        PDFRenderer pdfRenderer = new PDFRenderer(document);
+
+        try (ByteArrayOutputStream cbrOutputStream = new ByteArrayOutputStream();
+                ZipOutputStream zipOut = new ZipOutputStream(cbrOutputStream)) {
+
+            int totalPages = document.getNumberOfPages();
+
+            for (int pageIndex = 0; pageIndex < totalPages; pageIndex++) {
+                try {
+                    BufferedImage image =
+                            pdfRenderer.renderImageWithDPI(pageIndex, dpi, ImageType.RGB);
+
+                    String imageFilename = String.format("page_%03d.png", pageIndex + 1);
+
+                    ZipEntry zipEntry = new ZipEntry(imageFilename);
+                    zipOut.putNextEntry(zipEntry);
+
+                    ImageIO.write(image, "PNG", zipOut);
+                    zipOut.closeEntry();
+
+                } catch (IOException e) {
+                    log.warn("Error processing page {}: {}", pageIndex + 1, e.getMessage());
+                } catch (OutOfMemoryError e) {
+                    throw ExceptionUtils.createOutOfMemoryDpiException(pageIndex + 1, dpi, e);
+                } catch (NegativeArraySizeException e) {
+                    throw ExceptionUtils.createOutOfMemoryDpiException(pageIndex + 1, dpi, e);
+                }
+            }
+
+            zipOut.finish();
+            return cbrOutputStream.toByteArray();
+        }
+    }
+
+    public static boolean isPdfFile(MultipartFile file) {
+        String filename = file.getOriginalFilename();
+        if (filename == null) {
+            return false;
+        }
+
+        String extension = FilenameUtils.getExtension(filename).toLowerCase();
+        return "pdf".equals(extension);
+    }
+}

app/common/src/main/java/stirling/software/common/util/RegexPatternUtils.java

@@ -437,6 +437,11 @@ public final class RegexPatternUtils {
                 Pattern.CASE_INSENSITIVE);
     }
 
+    /** Pattern for matching image file extensions (case-insensitive) */
+    public Pattern getImageFilePattern() {
+        return getPattern(".*\\.(jpg|jpeg|png|gif|bmp|webp)$", Pattern.CASE_INSENSITIVE);
+    }
+
     /** Pattern for matching attachment section headers (case-insensitive) */
     public Pattern getAttachmentSectionPattern() {
         return getPattern("attachments\\s*\\(\\d+\\)", Pattern.CASE_INSENSITIVE);

app/core/src/main/java/stirling/software/SPDF/controller/api/converters/ConvertImgPDFController.java

@@ -8,6 +8,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
 import java.util.zip.ZipEntry;
@@ -32,15 +33,20 @@ import io.swagger.v3.oas.annotations.tags.Tag;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 
+import stirling.software.SPDF.config.EndpointConfiguration;
+import stirling.software.SPDF.model.api.converters.ConvertCbrToPdfRequest;
 import stirling.software.SPDF.model.api.converters.ConvertCbzToPdfRequest;
+import stirling.software.SPDF.model.api.converters.ConvertPdfToCbrRequest;
 import stirling.software.SPDF.model.api.converters.ConvertPdfToCbzRequest;
 import stirling.software.SPDF.model.api.converters.ConvertToImageRequest;
 import stirling.software.SPDF.model.api.converters.ConvertToPdfRequest;
 import stirling.software.common.service.CustomPDFDocumentFactory;
+import stirling.software.common.util.CbrUtils;
 import stirling.software.common.util.CbzUtils;
 import stirling.software.common.util.CheckProgramInstall;
 import stirling.software.common.util.ExceptionUtils;
 import stirling.software.common.util.GeneralUtils;
+import stirling.software.common.util.PdfToCbrUtils;
 import stirling.software.common.util.PdfToCbzUtils;
 import stirling.software.common.util.PdfUtils;
 import stirling.software.common.util.ProcessExecutor;
@@ -58,10 +64,15 @@ public class ConvertImgPDFController {
 
     private final CustomPDFDocumentFactory pdfDocumentFactory;
     private final TempFileManager tempFileManager;
+    private final EndpointConfiguration endpointConfiguration;
     private static final Pattern EXTENSION_PATTERN =
             RegexPatternUtils.getInstance().getPattern(RegexPatternUtils.getExtensionRegex());
     private static final String DEFAULT_COMIC_NAME = "comic";
 
+    private boolean isGhostscriptEnabled() {
+        return endpointConfiguration.isGroupEnabled("Ghostscript");
+    }
+
     @PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE, value = "/pdf/img")
     @Operation(
             summary = "Convert PDF to image(s)",
@@ -257,17 +268,29 @@ public class ConvertImgPDFController {
             description =
                     "This endpoint converts a CBZ (ZIP) comic book archive to a PDF file. "
                             + "Input:CBZ Output:PDF Type:SISO")
-    public ResponseEntity<byte[]> convertCbzToPdf(@ModelAttribute ConvertCbzToPdfRequest request)
+    public ResponseEntity<?> convertCbzToPdf(@ModelAttribute ConvertCbzToPdfRequest request)
             throws IOException {
         MultipartFile file = request.getFileInput();
+        boolean optimizeForEbook = request.isOptimizeForEbook();
+
+        // Disable optimization if Ghostscript is not available
+        if (optimizeForEbook && !isGhostscriptEnabled()) {
+            log.warn("Ghostscript optimization requested but Ghostscript is not enabled/available");
+            optimizeForEbook = false;
+        }
+
         byte[] pdfBytes;
         try {
-            pdfBytes = CbzUtils.convertCbzToPdf(file, pdfDocumentFactory, tempFileManager);
+            pdfBytes =
+                    CbzUtils.convertCbzToPdf(
+                            file, pdfDocumentFactory, tempFileManager, optimizeForEbook);
         } catch (IllegalArgumentException ex) {
             String message = ex.getMessage() == null ? "Invalid CBZ file" : ex.getMessage();
+            Map<String, Object> errorBody =
+                    Map.of("error", "Invalid CBZ file", "message", message, "trace", "");
             return ResponseEntity.status(HttpStatus.BAD_REQUEST)
-                    .contentType(MediaType.TEXT_PLAIN)
-                    .body(message.getBytes(java.nio.charset.StandardCharsets.UTF_8));
+                    .contentType(MediaType.APPLICATION_JSON)
+                    .body(errorBody);
         }
 
         String filename = createConvertedFilename(file.getOriginalFilename(), "_converted.pdf");
@@ -281,12 +304,12 @@ public class ConvertImgPDFController {
             description =
                     "This endpoint converts a PDF file to a CBZ (ZIP) comic book archive. "
                             + "Input:PDF Output:CBZ Type:SISO")
-    public ResponseEntity<byte[]> convertPdfToCbz(@ModelAttribute ConvertPdfToCbzRequest request)
+    public ResponseEntity<?> convertPdfToCbz(@ModelAttribute ConvertPdfToCbzRequest request)
             throws IOException {
         MultipartFile file = request.getFileInput();
-        Integer dpi = request.getDpi();
+        int dpi = request.getDpi();
 
-        if (dpi == null || dpi <= 0) {
+        if (dpi <= 0) {
             dpi = 300;
         }
 
@@ -295,9 +318,11 @@ public class ConvertImgPDFController {
             cbzBytes = PdfToCbzUtils.convertPdfToCbz(file, dpi, pdfDocumentFactory);
         } catch (IllegalArgumentException ex) {
             String message = ex.getMessage() == null ? "Invalid PDF file" : ex.getMessage();
+            Map<String, Object> errorBody =
+                    Map.of("error", "Invalid PDF file", "message", message, "trace", "");
             return ResponseEntity.status(HttpStatus.BAD_REQUEST)
-                    .contentType(MediaType.TEXT_PLAIN)
-                    .body(message.getBytes(java.nio.charset.StandardCharsets.UTF_8));
+                    .contentType(MediaType.APPLICATION_JSON)
+                    .body(errorBody);
         }
 
         String filename = createConvertedFilename(file.getOriginalFilename(), "_converted.cbz");
@@ -306,6 +331,75 @@ public class ConvertImgPDFController {
                 cbzBytes, filename, MediaType.APPLICATION_OCTET_STREAM);
     }
 
+    @PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE, value = "/cbr/pdf")
+    @Operation(
+            summary = "Convert CBR comic book archive to PDF",
+            description =
+                    "This endpoint converts a CBR (RAR) comic book archive to a PDF file. "
+                            + "Input:CBR Output:PDF Type:SISO")
+    public ResponseEntity<?> convertCbrToPdf(@ModelAttribute ConvertCbrToPdfRequest request)
+            throws IOException {
+        MultipartFile file = request.getFileInput();
+        boolean optimizeForEbook = request.isOptimizeForEbook();
+
+        // Disable optimization if Ghostscript is not available
+        if (optimizeForEbook && !isGhostscriptEnabled()) {
+            log.warn("Ghostscript optimization requested but Ghostscript is not enabled/available");
+            optimizeForEbook = false;
+        }
+
+        byte[] pdfBytes;
+        try {
+            pdfBytes =
+                    CbrUtils.convertCbrToPdf(
+                            file, pdfDocumentFactory, tempFileManager, optimizeForEbook);
+        } catch (IllegalArgumentException ex) {
+            String message = ex.getMessage() == null ? "Invalid CBR file" : ex.getMessage();
+            Map<String, Object> errorBody =
+                    Map.of("error", "Invalid CBR file", "message", message, "trace", "");
+            return ResponseEntity.status(HttpStatus.BAD_REQUEST)
+                    .contentType(MediaType.APPLICATION_JSON)
+                    .body(errorBody);
+        }
+
+        String filename = createConvertedFilename(file.getOriginalFilename(), "_converted.pdf");
+
+        return WebResponseUtils.bytesToWebResponse(pdfBytes, filename);
+    }
+
+    @PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE, value = "/pdf/cbr")
+    @Operation(
+            summary = "Convert PDF to CBR comic book archive",
+            description =
+                    "This endpoint converts a PDF file to a CBR-like (ZIP-based) comic book archive. "
+                            + "Note: Output is ZIP-based for compatibility. Input:PDF Output:CBR Type:SISO")
+    public ResponseEntity<?> convertPdfToCbr(@ModelAttribute ConvertPdfToCbrRequest request)
+            throws IOException {
+        MultipartFile file = request.getFileInput();
+        int dpi = request.getDpi();
+
+        if (dpi <= 0) {
+            dpi = 300;
+        }
+
+        byte[] cbrBytes;
+        try {
+            cbrBytes = PdfToCbrUtils.convertPdfToCbr(file, dpi, pdfDocumentFactory);
+        } catch (IllegalArgumentException ex) {
+            String message = ex.getMessage() == null ? "Invalid PDF file" : ex.getMessage();
+            Map<String, Object> errorBody =
+                    Map.of("error", "Invalid PDF file", "message", message, "trace", "");
+            return ResponseEntity.status(HttpStatus.BAD_REQUEST)
+                    .contentType(MediaType.APPLICATION_JSON)
+                    .body(errorBody);
+        }
+
+        String filename = createConvertedFilename(file.getOriginalFilename(), "_converted.cbr");
+
+        return WebResponseUtils.bytesToWebResponse(
+                cbrBytes, filename, MediaType.APPLICATION_OCTET_STREAM);
+    }
+
     private String createConvertedFilename(String originalFilename, String suffix) {
         if (originalFilename == null) {
             return GeneralUtils.generateFilename(DEFAULT_COMIC_NAME, suffix);

app/core/src/main/java/stirling/software/SPDF/controller/web/ConverterWebController.java

@@ -37,6 +37,20 @@ public class ConverterWebController {
         return "convert/pdf-to-cbz";
     }
 
+    @GetMapping("/cbr-to-pdf")
+    @Hidden
+    public String convertCbrToPdfForm(Model model) {
+        model.addAttribute("currentPage", "cbr-to-pdf");
+        return "convert/cbr-to-pdf";
+    }
+
+    @GetMapping("/pdf-to-cbr")
+    @Hidden
+    public String convertPdfToCbrForm(Model model) {
+        model.addAttribute("currentPage", "pdf-to-cbr");
+        return "convert/pdf-to-cbr";
+    }
+
     @GetMapping("/html-to-pdf")
     @Hidden
     public String convertHTMLToPdfForm(Model model) {

app/core/src/main/java/stirling/software/SPDF/model/api/converters/ConvertCbrToPdfRequest.java

@@ -0,0 +1,23 @@
+package stirling.software.SPDF.model.api.converters;
+
+import org.springframework.web.multipart.MultipartFile;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+
+@Data
+@EqualsAndHashCode
+public class ConvertCbrToPdfRequest {
+
+    @Schema(
+            description = "The input CBR file to be converted to a PDF file",
+            requiredMode = Schema.RequiredMode.REQUIRED)
+    private MultipartFile fileInput;
+
+    @Schema(
+            description = "Optimize the output PDF for ebook reading using Ghostscript",
+            defaultValue = "false")
+    private boolean optimizeForEbook;
+}

app/core/src/main/java/stirling/software/SPDF/model/api/converters/ConvertCbzToPdfRequest.java

@@ -15,4 +15,9 @@ public class ConvertCbzToPdfRequest {
             description = "The input CBZ file to be converted to a PDF file",
             requiredMode = Schema.RequiredMode.REQUIRED)
     private MultipartFile fileInput;
+
+    @Schema(
+            description = "Optimize the output PDF for ebook reading using Ghostscript",
+            defaultValue = "false")
+    private boolean optimizeForEbook;
 }

app/core/src/main/java/stirling/software/SPDF/model/api/converters/ConvertPdfToCbrRequest.java

@@ -0,0 +1,24 @@
+package stirling.software.SPDF.model.api.converters;
+
+import org.springframework.web.multipart.MultipartFile;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+
+@Data
+@EqualsAndHashCode
+public class ConvertPdfToCbrRequest {
+
+    @Schema(
+            description = "The input PDF file to be converted to a CBR file",
+            requiredMode = Schema.RequiredMode.REQUIRED)
+    private MultipartFile fileInput;
+
+    @Schema(
+            description = "The DPI (Dots Per Inch) for rendering PDF pages as images",
+            example = "150",
+            requiredMode = Schema.RequiredMode.REQUIRED)
+    private int dpi = 150;
+}

app/core/src/main/java/stirling/software/SPDF/model/api/converters/ConvertPdfToCbzRequest.java

@@ -18,7 +18,7 @@ public class ConvertPdfToCbzRequest {
 
     @Schema(
             description = "The DPI (Dots Per Inch) for rendering PDF pages as images",
-            example = "300",
-            requiredMode = Schema.RequiredMode.NOT_REQUIRED)
-    private Integer dpi = 300;
+            example = "150",
+            requiredMode = Schema.RequiredMode.REQUIRED)
+    private int dpi = 150;
 }

app/core/src/main/resources/messages_en_GB.properties

@@ -610,10 +610,18 @@ home.cbzToPdf.title=CBZ to PDF
 home.cbzToPdf.desc=Convert CBZ comic book archives to PDF format.
 cbzToPdf.tags=conversion,comic,book,archive,cbz,zip
 
+home.cbrToPdf.title=CBR to PDF
+home.cbrToPdf.desc=Convert CBR comic book archives to PDF format.
+cbrToPdf.tags=conversion,comic,book,archive,cbr,rar
+
 home.pdfToCbz.title=PDF to CBZ
 home.pdfToCbz.desc=Convert PDF files to CBZ comic book archives.
 pdfToCbz.tags=conversion,comic,book,archive,cbz,pdf
 
+home.pdfToCbr.title=PDF to CBR
+home.pdfToCbr.desc=Convert PDF files to CBR comic book archives.
+pdfToCbr.tags=conversion,comic,book,archive,cbr,rar
+
 home.pdfToImage.title=PDF to Image
 home.pdfToImage.desc=Convert a PDF to a image. (PNG, JPEG, GIF, PSD)
 pdfToImage.tags=conversion,img,jpg,picture,photo,psd,photoshop
@@ -1445,6 +1453,7 @@ cbzToPDF.title=CBZ to PDF
 cbzToPDF.header=CBZ to PDF
 cbzToPDF.submit=Convert to PDF
 cbzToPDF.selectText=Select CBZ file
+cbzToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
 
 #pdfToCBZ
 pdfToCBZ.title=PDF to CBZ
@@ -1453,6 +1462,21 @@ pdfToCBZ.submit=Convert to CBZ
 pdfToCBZ.selectText=Select PDF file
 pdfToCBZ.dpi=DPI (Dots Per Inch)
 
+#cbrToPDF
+cbrToPDF.title=CBR to PDF
+cbrToPDF.header=CBR to PDF
+cbrToPDF.submit=Convert to PDF
+cbrToPDF.selectText=Select CBR file
+cbrToPDF.optimizeForEbook=Optimize PDF for ebook readers (uses Ghostscript)
+
+#pdfToCBR
+pdfToCBR.title=PDF to CBR
+pdfToCBR.header=PDF to CBR
+pdfToCBR.submit=Convert to CBR
+pdfToCBR.selectText=Select PDF file
+pdfToCBR.dpi=DPI (Dots Per Inch)
+pdfToCBR.dpiHelp=Higher DPI results in better quality but larger file size.
+
 #pdfToImage
 pdfToImage.title=PDF to Image
 pdfToImage.header=PDF to Image

app/core/src/main/resources/templates/convert/cbr-to-pdf.html

@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<html th:data-language="${#locale.toString()}" th:dir="#{language.direction}" th:lang="${#locale.language}"
+  xmlns:th="https://www.thymeleaf.org">
+
+<head>
+  <th:block th:insert="~{fragments/common :: head(title=#{cbrToPDF.title}, header=#{cbrToPDF.header})}"></th:block>
+</head>
+
+<body>
+  <th:block th:insert="~{fragments/common :: game}"></th:block>
+  <div id="page-container">
+    <div id="content-wrap">
+      <th:block th:insert="~{fragments/navbar.html :: navbar}"></th:block>
+      <br><br>
+      <div class="container">
+        <div class="row justify-content-center">
+          <div class="col-md-6 bg-card">
+            <div class="tool-header">
+              <span class="material-symbols-rounded tool-header-icon convertto">auto_stories</span>
+              <span class="tool-header-text" th:text="#{cbrToPDF.header}"></span>
+            </div>
+            <form enctype="multipart/form-data" id="cbrToPDFForm" method="post"
+              th:action="@{'/api/v1/convert/cbr/pdf'}">
+              <div
+                th:replace="~{fragments/common :: fileSelector(name='fileInput', multipleInputsForSingleRequest=false, accept='.cbr,.rar', inputText=#{cbrToPDF.selectText})}">
+              </div>
+              
+              <div class="form-check mb-3" th:if="${@endpointConfiguration.isGroupEnabled('Ghostscript')}">
+                <input id="optimizeForEbook" name="optimizeForEbook" type="checkbox" value="true">
+                <label for="optimizeForEbook" th:text="#{cbrToPDF.optimizeForEbook}">Optimize PDF for ebook readers (uses Ghostscript)</label>
+              </div>
+              
+              <br>
+              <button class="btn btn-primary" id="submitBtn" th:text="#{cbrToPDF.submit}" type="submit">Convert to PDF</button>
+            </form>
+          </div>
+        </div>
+      </div>
+    </div>
+    <th:block th:insert="~{fragments/footer.html :: footer}"></th:block>
+  </div>
+</body>
+
+</html>

app/core/src/main/resources/templates/convert/cbz-to-pdf.html

@@ -25,6 +25,11 @@
                 th:replace="~{fragments/common :: fileSelector(name='fileInput', multipleInputsForSingleRequest=false, accept='.cbz,.zip', inputText=#{cbzToPDF.selectText})}">
               </div>
               
+              <div class="form-check mb-3" th:if="${@endpointConfiguration.isGroupEnabled('Ghostscript')}">
+                <input id="optimizeForEbook" name="optimizeForEbook" type="checkbox" value="true">
+                <label for="optimizeForEbook" th:text="#{cbzToPDF.optimizeForEbook}">Optimize PDF for ebook readers (uses Ghostscript)</label>
+              </div>
+              
               <br>
               <button class="btn btn-primary" id="submitBtn" th:text="#{cbzToPDF.submit}" type="submit">Convert to PDF</button>
             </form>

app/core/src/main/resources/templates/convert/pdf-to-cbr.html

@@ -0,0 +1,45 @@
+<!DOCTYPE html>
+<html th:data-language="${#locale.toString()}" th:dir="#{language.direction}" th:lang="${#locale.language}"
+  xmlns:th="https://www.thymeleaf.org">
+
+<head>
+  <th:block th:insert="~{fragments/common :: head(title=#{pdfToCBR.title}, header=#{pdfToCBR.header})}"></th:block>
+</head>
+
+<body>
+  <th:block th:insert="~{fragments/common :: game}"></th:block>
+  <div id="page-container">
+    <div id="content-wrap">
+      <th:block th:insert="~{fragments/navbar.html :: navbar}"></th:block>
+      <br><br>
+      <div class="container">
+        <div class="row justify-content-center">
+          <div class="col-md-6 bg-card">
+            <div class="tool-header">
+              <span class="material-symbols-rounded tool-header-icon convertto">auto_stories</span>
+              <span class="tool-header-text" th:text="#{pdfToCBR.header}"></span>
+            </div>
+            <form enctype="multipart/form-data" id="pdfToCBRForm" method="post"
+              th:action="@{'/api/v1/convert/pdf/cbr'}">
+              <div
+                th:replace="~{fragments/common :: fileSelector(name='fileInput', multipleInputsForSingleRequest=false, accept='.pdf', inputText=#{pdfToCBR.selectText})}">
+              </div>
+              
+              <div class="mb-3">
+                <label class="form-label" for="dpi" th:text="#{pdfToCBR.dpi}">DPI:</label>
+                <input class="form-control" id="dpi" max="600" min="50" name="dpi" type="number" value="300">
+                <div class="form-text" th:text="#{pdfToCBR.dpiHelp}">Higher DPI results in better quality but larger file size.</div>
+              </div>
+              
+              <br>
+              <button class="btn btn-primary" id="submitBtn" th:text="#{pdfToCBR.submit}" type="submit">Convert to CBR</button>
+            </form>
+          </div>
+        </div>
+      </div>
+    </div>
+    <th:block th:insert="~{fragments/footer.html :: footer}"></th:block>
+  </div>
+</body>
+
+</html>

app/core/src/main/resources/templates/fragments/navElements.html

@@ -50,6 +50,9 @@
       <div
         th:replace="~{fragments/navbarEntry :: navbarEntry('cbz-to-pdf', 'auto_stories', 'home.cbzToPdf.title', 'home.cbzToPdf.desc', 'cbzToPdf.tags', 'convertto')}">
       </div>
+      <div
+        th:replace="~{fragments/navbarEntry :: navbarEntry('cbr-to-pdf', 'auto_stories', 'home.cbrToPdf.title', 'home.cbrToPdf.desc', 'cbrToPdf.tags', 'convertto')}">
+      </div>
       <div
         th:replace="~{fragments/navbarEntry :: navbarEntry('file-to-pdf', 'draft', 'home.fileToPDF.title', 'home.fileToPDF.desc', 'fileToPDF.tags', 'convertto')}">
       </div>
@@ -77,6 +80,9 @@
       <div
         th:replace="~{fragments/navbarEntry :: navbarEntry('pdf-to-cbz', 'auto_stories', 'home.pdfToCbz.title', 'home.pdfToCbz.desc', 'pdfToCbz.tags', 'convert')}">
       </div>
+      <div
+        th:replace="~{fragments/navbarEntry :: navbarEntry('pdf-to-cbr', 'auto_stories', 'home.pdfToCbr.title', 'home.pdfToCbr.desc', 'pdfToCbr.tags', 'convert')}">
+      </div>
       <div
         th:replace="~{fragments/navbarEntry :: navbarEntry('pdf-to-pdfa', 'picture_as_pdf', 'home.pdfToPDFA.title', 'home.pdfToPDFA.desc', 'pdfToPDFA.tags', 'convert')}">
       </div>
@@ -114,6 +120,9 @@
       <div
         th:replace="~{fragments/navbarEntry :: navbarEntry('cbz-to-pdf', 'auto_stories', 'home.cbzToPdf.title', 'home.cbzToPdf.desc', 'cbzToPdf.tags', 'convertto')}">
       </div>
+      <div
+        th:replace="~{fragments/navbarEntry :: navbarEntry('cbr-to-pdf', 'auto_stories', 'home.cbrToPdf.title', 'home.cbrToPdf.desc', 'cbrToPdf.tags', 'convertto')}">
+      </div>
       <div
         th:replace="~{fragments/navbarEntry :: navbarEntry('file-to-pdf', 'draft', 'home.fileToPDF.title', 'home.fileToPDF.desc', 'fileToPDF.tags', 'convertto')}">
       </div>

app/core/src/test/java/stirling/software/SPDF/controller/api/converters/CbrUtilsTest.java

@@ -0,0 +1,91 @@
+package stirling.software.SPDF.controller.api.converters;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.mock.web.MockMultipartFile;
+
+import stirling.software.common.util.CbrUtils;
+
+class CbrUtilsTest {
+
+    @Test
+    void testIsCbrFile_ValidCbrFile() {
+        MockMultipartFile cbrFile =
+                new MockMultipartFile(
+                        "file",
+                        "test.cbr",
+                        "application/x-rar-compressed",
+                        "test content".getBytes());
+
+        assertTrue(CbrUtils.isCbrFile(cbrFile));
+    }
+
+    @Test
+    void testIsCbrFile_ValidRarFile() {
+        MockMultipartFile rarFile =
+                new MockMultipartFile(
+                        "file",
+                        "test.rar",
+                        "application/x-rar-compressed",
+                        "test content".getBytes());
+
+        assertTrue(CbrUtils.isCbrFile(rarFile));
+    }
+
+    @Test
+    void testIsCbrFile_InvalidFile() {
+        MockMultipartFile textFile =
+                new MockMultipartFile("file", "test.txt", "text/plain", "test content".getBytes());
+
+        assertFalse(CbrUtils.isCbrFile(textFile));
+    }
+
+    @Test
+    void testIsCbrFile_NoFilename() {
+        MockMultipartFile noNameFile =
+                new MockMultipartFile(
+                        "file", null, "application/x-rar-compressed", "test content".getBytes());
+
+        assertFalse(CbrUtils.isCbrFile(noNameFile));
+    }
+
+    @Test
+    void testIsCbrFile_PdfFile() {
+        MockMultipartFile pdfFile =
+                new MockMultipartFile(
+                        "file", "document.pdf", "application/pdf", "pdf content".getBytes());
+
+        assertFalse(CbrUtils.isCbrFile(pdfFile));
+    }
+
+    @Test
+    void testIsCbrFile_JpegFile() {
+        MockMultipartFile jpegFile =
+                new MockMultipartFile("file", "image.jpg", "image/jpeg", "jpeg content".getBytes());
+
+        assertFalse(CbrUtils.isCbrFile(jpegFile));
+    }
+
+    @Test
+    void testIsCbrFile_ZipFile() {
+        MockMultipartFile zipFile =
+                new MockMultipartFile(
+                        "file", "archive.zip", "application/zip", "zip content".getBytes());
+
+        assertFalse(CbrUtils.isCbrFile(zipFile));
+    }
+
+    @Test
+    void testIsCbrFile_MixedCaseExtension() {
+        MockMultipartFile cbrFile =
+                new MockMultipartFile(
+                        "file",
+                        "test.CBR",
+                        "application/x-rar-compressed",
+                        "test content".getBytes());
+
+        assertTrue(CbrUtils.isCbrFile(cbrFile));
+    }
+}