How can I remove all images/drawings from a PDF file and leave text only in Java?

Question

I have a PDF file that\'s an output from an OCR processor, this OCR processor recognizes the image, adds the text to the pdf but at the end places a low quality image instea

Answer 1

You need to parse the document as follows:

public static void strip(String pdfFile, String pdfFileOut) throws Exception {

    PDDocument doc = PDDocument.load(pdfFile);

    List pages = doc.getDocumentCatalog().getAllPages();
    for( int i=0; i<pages.size(); i++ ) {
        PDPage page = (PDPage)pages.get( i );

        // added
        COSDictionary newDictionary = new COSDictionary(page.getCOSDictionary());

        PDFStreamParser parser = new PDFStreamParser(page.getContents());
        parser.parse();
        List tokens = parser.getTokens();
        List newTokens = new ArrayList();
        for(int j=0; j<tokens.size(); j++) {
            Object token = tokens.get( j );

            if( token instanceof PDFOperator ) {
                PDFOperator op = (PDFOperator)token;
                if( op.getOperation().equals( "Do") ) {
                    //remove the one argument to this operator
                    // added
                    COSName name = (COSName)newTokens.remove( newTokens.size() -1 );
                    // added
                    deleteObject(newDictionary, name);
                    continue;
                }
            }
            newTokens.add( token );
        }
        PDStream newContents = new PDStream( doc );
        ContentStreamWriter writer = new ContentStreamWriter( newContents.createOutputStream() );
        writer.writeTokens( newTokens );
        newContents.addCompression();

        page.setContents( newContents );

        // added
        PDResources newResources = new PDResources(newDictionary);
        page.setResources(newResources);
    }

    doc.save(pdfFileOut);
    doc.close();
}


// added
public static boolean deleteObject(COSDictionary d, COSName name) {
    for(COSName key : d.keySet()) {
        if( name.equals(key) ) {
            d.removeItem(key);
            return true;
        }
        COSBase object = d.getDictionaryObject(key); 
        if(object instanceof COSDictionary) {
            if( deleteObject((COSDictionary)object, name) ) {
                return true;
            }
        }
    }
    return false;
}

Answer 2

I used Apache PDFBox in similar situation.

To be a little bit more specific, try something like that:

import org.apache.pdfbox.exceptions.COSVisitorException;
import org.apache.pdfbox.exceptions.CryptographyException;
import org.apache.pdfbox.exceptions.InvalidPasswordException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDDocumentCatalog;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDResources;
import java.io.IOException;

public class Main {
    public static void main(String[] argv) throws COSVisitorException, InvalidPasswordException, CryptographyException, IOException {
        PDDocument document = PDDocument.load("input.pdf");

        if (document.isEncrypted()) {
            document.decrypt("");
        }

        PDDocumentCatalog catalog = document.getDocumentCatalog();
        for (Object pageObj :  catalog.getAllPages()) {
            PDPage page = (PDPage) pageObj;
            PDResources resources = page.findResources();
            resources.getImages().clear();
        }

        document.save("strippedOfImages.pdf");
    }
}

It's supposed to remove all types of images (png, jpeg, ...). It should work like that:

.