/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.pdfbox.examples.util;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

import org.apache.pdfbox.contentstream.PDContentStream;
import org.apache.pdfbox.contentstream.operator.Operator;
import org.apache.pdfbox.cos.COSName;
import org.apache.pdfbox.pdfparser.PDFStreamParser;
import org.apache.pdfbox.pdfwriter.ContentStreamWriter;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDResources;
import org.apache.pdfbox.pdmodel.common.PDStream;
import org.apache.pdfbox.pdmodel.graphics.PDXObject;
import org.apache.pdfbox.pdmodel.graphics.form.PDFormXObject;
import org.apache.pdfbox.pdmodel.graphics.pattern.PDAbstractPattern;
import org.apache.pdfbox.pdmodel.graphics.pattern.PDTilingPattern;

/**
 * This is an example on how to remove all text from PDF document.
 *
 * @author Ben Litchfield
 */
public final class RemoveAllText
{
    /**
     * Default constructor.
     */
    private RemoveAllText()
    {
        // example class should not be instantiated
    }

    /**
     * This will remove all text from a PDF document.
     *
     * @param args The command line arguments.
     *
     * @throws IOException If there is an error parsing the document.
     */
    public static void main(String[] args) throws IOException
    {
        if (args.length != 2)
        {
            usage();
        }
        else
        {
            try (PDDocument document = PDDocument.load(new File(args[0])))
            {
                if (document.isEncrypted())
                {
                    System.err.println(
                            "Error: Encrypted documents are not supported for this example.");
                    System.exit(1);
                }
                for (PDPage page : document.getPages())
                {
                    List<Object> newTokens = createTokensWithoutText(page);
                    PDStream newContents = new PDStream(document);
                    writeTokensToStream(newContents, newTokens);
                    page.setContents(newContents);
                    processResources(page.getResources());
                }
                document.save(args[1]);
            }
        }
    }

    private static void processResources(PDResources resources) throws IOException
    {
        for (COSName name : resources.getXObjectNames())
        {
            PDXObject xobject = resources.getXObject(name);
            if (xobject instanceof PDFormXObject)
            {
                PDFormXObject formXObject = (PDFormXObject) xobject;
                writeTokensToStream(formXObject.getContentStream(),
                        createTokensWithoutText(formXObject));
                processResources(formXObject.getResources());
            }
        }
        for (COSName name : resources.getPatternNames())
        {
            PDAbstractPattern pattern = resources.getPattern(name);
            if (pattern instanceof PDTilingPattern)
            {
                PDTilingPattern tilingPattern = (PDTilingPattern) pattern;
                writeTokensToStream(tilingPattern.getContentStream(),
                        createTokensWithoutText(tilingPattern));
                processResources(tilingPattern.getResources());
            }
        }
    }

    private static void writeTokensToStream(PDStream newContents, List<Object> newTokens) throws IOException
    {
        try (OutputStream out = newContents.createOutputStream(COSName.FLATE_DECODE))
        {
            ContentStreamWriter writer = new ContentStreamWriter(out);
            writer.writeTokens(newTokens);
        }
    }

    private static List<Object> createTokensWithoutText(PDContentStream contentStream) throws IOException
    {
        PDFStreamParser parser = new PDFStreamParser(contentStream.getContents());
        Object token = parser.parseNextToken();
        List<Object> newTokens = new ArrayList<>();
        while (token != null)
        {
            if (token instanceof Operator)
            {
                Operator op = (Operator) token;
                if ("TJ".equals(op.getName()) || "Tj".equals(op.getName()) ||
                    "'".equals(op.getName()) || "\"".equals(op.getName()))
                {
                    // remove the one argument to this operator
                    newTokens.remove(newTokens.size() - 1);
                    
                    token = parser.parseNextToken();
                    continue;
                }
            }
            newTokens.add(token);
            token = parser.parseNextToken();
        }
        return newTokens;
    }

    /**
     * This will print the usage for this document.
     */
    private static void usage()
    {
        System.err.println(
                "Usage: java " + RemoveAllText.class.getName() + " <input-pdf> <output-pdf>");
    }

}

@@ -5024,16 +5024,36 @@
 me()) %7C%7C
+%0A                   
  %22Tj%22.eq
@@ -5122,12 +5122,275 @@
 e())
- %7C%7C 
+)%0A                %7B%0A                    // remove the argument to this operator%0A                    newTokens.remove(newTokens.size() - 1);%0A%0A                    token = parser.parseNextToken();%0A                    continue;%0A                %7D%0A                else if (
 %22%5C%22%22
@@ -5464,19 +5464,17 @@
 ove the 
-one
+3
  argumen
@@ -5466,32 +5466,33 @@
 e the 3 argument
+s
  to this operato
@@ -5573,16 +5573,116 @@
         
+newTokens.remove(newTokens.size() - 1);%0A                    newTokens.remove(newTokens.size() - 1);%0A
 %0A       

delete all 3 parameters of with " operator, thanks Michael Klink