Feature: Split PDFs by Chapters/Bookmarks (#1786)

* feature:split pdf by chapters

* Update SplitPdfByChaptersController.java

* Update SplitPdfByChaptersController.java

* Update SplitPdfByChaptersController.java
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package stirling.software.SPDF.controller.api;
import java.io.ByteArrayOutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
import org.apache.pdfbox.Loader;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.interactive.documentnavigation.outline.PDDocumentOutline;
import org.apache.pdfbox.pdmodel.interactive.documentnavigation.outline.PDOutlineItem;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import io.github.pixee.security.Filenames;
import io.swagger.v3.oas.annotations.Operation;
import io.swagger.v3.oas.annotations.tags.Tag;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
import stirling.software.SPDF.model.PdfMetadata;
import stirling.software.SPDF.model.api.SplitPdfByChaptersRequest;
import stirling.software.SPDF.utils.PdfUtils;
import stirling.software.SPDF.utils.WebResponseUtils;
@RestController
@RequestMapping("/api/v1/general")
@Tag(name = "General", description = "General APIs")
public class SplitPdfByChaptersController {
private static final Logger logger =
LoggerFactory.getLogger(SplitPdfByChaptersController.class);
@PostMapping(value = "/split-pdf-by-chapters", consumes = "multipart/form-data")
@Operation(
summary = "Split PDFs by Chapters",
description = "Splits a PDF into chapters and returns a ZIP file.")
public ResponseEntity<byte[]> splitPdf(@ModelAttribute SplitPdfByChaptersRequest request)
throws Exception {
MultipartFile file = request.getFileInput();
boolean includeMetadata = request.getIncludeMetadata();
Integer bookmarkLevel =
request.getBookmarkLevel(); // levels start from 0 (top most bookmarks)
if (bookmarkLevel < 0) {
return ResponseEntity.badRequest().body("Invalid bookmark level".getBytes());
}
PDDocument sourceDocument = Loader.loadPDF(file.getBytes());
// checks if the document is encrypted by an empty user password
if (sourceDocument.isEncrypted()) {
try {
sourceDocument.setAllSecurityToBeRemoved(true);
logger.info("Removing security from the source document ");
} catch (Exception e) {
logger.warn("Cannot decrypt the pdf");
}
}
PDDocumentOutline outline = sourceDocument.getDocumentCatalog().getDocumentOutline();
if (outline == null) {
logger.warn("No outline found for {}", file.getOriginalFilename());
return ResponseEntity.badRequest().body("No outline found".getBytes());
}
List<Bookmark> bookmarks = new ArrayList<>();
try {
bookmarks =
extractOutlineItems(
sourceDocument,
outline.getFirstChild(),
bookmarks,
outline.getFirstChild().getNextSibling(),
0,
bookmarkLevel);
// to handle last page edge case
bookmarks.get(bookmarks.size() - 1).setEndPage(sourceDocument.getNumberOfPages());
Bookmark lastBookmark = bookmarks.get(bookmarks.size() - 1);
} catch (Exception e) {
logger.error("Unable to extract outline items", e);
return ResponseEntity.internalServerError()
.body("Unable to extract outline items".getBytes());
}
boolean allowDuplicates = request.getAllowDuplicates();
if (!allowDuplicates) {
/*
duplicates are generated when multiple bookmarks correspond to the same page,
if the user doesn't want duplicates mergeBookmarksThatCorrespondToSamePage() method will merge the titles of all
the bookmarks that correspond to the same page, and treat them as a single bookmark
*/
bookmarks = mergeBookmarksThatCorrespondToSamePage(bookmarks);
}
for (Bookmark bookmark : bookmarks) {
logger.info(
"{}::::{} to {}",
bookmark.getTitle(),
bookmark.getStartPage(),
bookmark.getEndPage());
}
List<ByteArrayOutputStream> splitDocumentsBoas =
getSplitDocumentsBoas(sourceDocument, bookmarks, includeMetadata);
Path zipFile = createZipFile(bookmarks, splitDocumentsBoas);
byte[] data = Files.readAllBytes(zipFile);
Files.deleteIfExists(zipFile);
String filename =
Filenames.toSimpleFileName(file.getOriginalFilename())
.replaceFirst("[.][^.]+$", "");
sourceDocument.close();
return WebResponseUtils.bytesToWebResponse(
data, filename + ".zip", MediaType.APPLICATION_OCTET_STREAM);
}
private List<Bookmark> mergeBookmarksThatCorrespondToSamePage(List<Bookmark> bookmarks) {
String mergedTitle = "";
List<Bookmark> chaptersToBeRemoved = new ArrayList<>();
for (Bookmark bookmark : bookmarks) {
if (bookmark.getStartPage() == bookmark.getEndPage()) {
mergedTitle = mergedTitle.concat(bookmark.getTitle().concat(" "));
chaptersToBeRemoved.add(bookmark);
} else {
if (!mergedTitle.isEmpty()) {
if (mergedTitle.length() > 255) {
mergedTitle = mergedTitle.substring(0, 253) + "...";
}
bookmarks.set(
bookmarks.indexOf(bookmark),
new Bookmark(
mergedTitle, bookmark.getStartPage(), bookmark.getEndPage()));
}
mergedTitle = "";
}
}
bookmarks.removeAll(chaptersToBeRemoved);
return bookmarks;
}
private static List<Bookmark> extractOutlineItems(
PDDocument sourceDocument,
PDOutlineItem current,
List<Bookmark> bookmarks,
PDOutlineItem nextParent,
int level,
int maxLevel)
throws Exception {
while (current != null) {
String currentTitle = current.getTitle().replace("/", "");
int firstPage =
sourceDocument.getPages().indexOf(current.findDestinationPage(sourceDocument));
PDOutlineItem child = current.getFirstChild();
PDOutlineItem nextSibling = current.getNextSibling();
int endPage;
if (child != null && level < maxLevel) {
endPage =
sourceDocument
.getPages()
.indexOf(child.findDestinationPage(sourceDocument));
} else if (nextSibling != null) {
endPage =
sourceDocument
.getPages()
.indexOf(nextSibling.findDestinationPage(sourceDocument));
} else if (nextParent != null) {
endPage =
sourceDocument
.getPages()
.indexOf(nextParent.findDestinationPage(sourceDocument));
} else {
endPage = -2;
/*
happens when we have something like this:
Outline Item 2
Outline Item 2.1
Outline Item 2.1.1
Outline Item 2.2
Outline 2.2.1
Outline 2.2.2 <--- this item neither has an immediate next parent nor an immediate next sibling
Outline Item 3
*/
}
if (!bookmarks.isEmpty()
&& bookmarks.get(bookmarks.size() - 1).getEndPage() == -2
&& firstPage
>= bookmarks
.get(bookmarks.size() - 1)
.getStartPage()) { // for handling the above-mentioned case
Bookmark previousBookmark = bookmarks.get(bookmarks.size() - 1);
previousBookmark.setEndPage(firstPage);
}
bookmarks.add(new Bookmark(currentTitle, firstPage, endPage));
// Recursively process children
if (child != null && level < maxLevel) {
extractOutlineItems(
sourceDocument, child, bookmarks, nextSibling, level + 1, maxLevel);
}
current = nextSibling;
}
return bookmarks;
}
private Path createZipFile(
List<Bookmark> bookmarks, List<ByteArrayOutputStream> splitDocumentsBoas)
throws Exception {
Path zipFile = Files.createTempFile("split_documents", ".zip");
String fileNumberFormatter = "%0" + (Integer.toString(bookmarks.size()).length()) + "d ";
try (ZipOutputStream zipOut = new ZipOutputStream(Files.newOutputStream(zipFile))) {
for (int i = 0; i < splitDocumentsBoas.size(); i++) {
// split files will be named as "[FILE_NUMBER] [BOOKMARK_TITLE].pdf"
String fileName =
String.format(fileNumberFormatter, i)
+ bookmarks.get(i).getTitle()
+ ".pdf";
ByteArrayOutputStream baos = splitDocumentsBoas.get(i);
byte[] pdf = baos.toByteArray();
ZipEntry pdfEntry = new ZipEntry(fileName);
zipOut.putNextEntry(pdfEntry);
zipOut.write(pdf);
zipOut.closeEntry();
logger.info("Wrote split document {} to zip file", fileName);
}
} catch (Exception e) {
logger.error("Failed writing to zip", e);
throw e;
}
logger.info("Successfully created zip file with split documents: {}", zipFile);
return zipFile;
}
public List<ByteArrayOutputStream> getSplitDocumentsBoas(
PDDocument sourceDocument, List<Bookmark> bookmarks, boolean includeMetadata)
throws Exception {
List<ByteArrayOutputStream> splitDocumentsBoas = new ArrayList<>();
PdfMetadata metadata = null;
if (includeMetadata) {
metadata = PdfUtils.extractMetadataFromPdf(sourceDocument);
}
for (Bookmark bookmark : bookmarks) {
try (PDDocument splitDocument = new PDDocument()) {
boolean isSinglePage = (bookmark.getStartPage() == bookmark.getEndPage());
for (int i = bookmark.getStartPage();
i < bookmark.getEndPage() + (isSinglePage ? 1 : 0);
i++) {
PDPage page = sourceDocument.getPage(i);
splitDocument.addPage(page);
logger.info("Adding page {} to split document", i);
}
ByteArrayOutputStream baos = new ByteArrayOutputStream();
if (includeMetadata) {
PdfUtils.setMetadataToPdf(splitDocument, metadata);
}
splitDocument.save(baos);
splitDocumentsBoas.add(baos);
} catch (Exception e) {
logger.error("Failed splitting documents and saving them", e);
throw e;
}
}
return splitDocumentsBoas;
}
}
@Data
@EqualsAndHashCode
@NoArgsConstructor
@AllArgsConstructor
class Bookmark {
private String title;
private int startPage;
private int endPage;
}

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package stirling.software.SPDF.model.api;
import io.swagger.v3.oas.annotations.media.Schema;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@EqualsAndHashCode(callSuper = false)
public class SplitPdfByChaptersRequest extends PDFFile {
@Schema(description = "Whether to include Metadata or not", example = "true")
private Boolean includeMetadata;
@Schema(description = "Whether to allow duplicates or not", example = "true")
private Boolean allowDuplicates;
@Schema(description = "Maximum bookmark level required", example = "2")
private Integer bookmarkLevel;
}