What Is fop.jar? I got it from the fop-2.7-bin.zip.

fop.jar in fop-2.7-bin.zip is the JAR file for FOP 2.7, which is a print formatter driven by XSL formatting objects (XSL-FO). You can obtain fop.jar from the build folder of the fop-2.7-bin.zip file.

Below is the information about the fop.jar (2.2) file:

JAR File Size and Download Location:

JAR name: fop.jar, fop-2.7.jar
Target JDK version: 1.7
File name: fop.jar
File size: 4442817 bytes
Release date: 20-Jan-2022
Download: Apache FOP Website

Java source code files for fop.jar:

⏎ org/apache/fop/afp/modca/PageDescriptor.java

/*
 * 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.
 */

/* $Id: PageDescriptor.java 1297404 2012-03-06 10:17:54Z vhennebert $ */

package org.apache.fop.afp.modca;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.fop.afp.util.BinaryUtils;

/**
 * The Page Descriptor structured field specifies the size and attributes of
 * a page or overlay presentation space.
 *
 */
public class PageDescriptor extends AbstractDescriptor {

    /**
     * Construct a page descriptor for the specified page width
     * and page height.
     *
     * @param width The page width.
     * @param height The page height.
     * @param widthRes The page width resolution
     * @param heightRes The page height resolution
     */
    public PageDescriptor(int width, int height, int widthRes, int heightRes) {
        super(width, height, widthRes, heightRes);
    }

    /** {@inheritDoc} */
    public void writeToStream(OutputStream os) throws IOException {
        byte[] data = new byte[24];
        copySF(data, Type.DESCRIPTOR, Category.PAGE);
        data[2] = 0x17;

        // XpgBase
        data[9] = 0x00; // XpgBase = 10 inches

        // YpgBase
        data[10] = 0x00; // YpgBase = 10 inches

        // XpgUnits
        byte[] xdpi = BinaryUtils.convert(widthRes * 10, 2);
        data[11] = xdpi[0];
        data[12] = xdpi[1];

        // YpgUnits
        byte[] ydpi = BinaryUtils.convert(heightRes * 10, 2);
        data[13] = ydpi[0];
        data[14] = ydpi[1];

        // XpgSize
        byte[] x = BinaryUtils.convert(width, 3);
        data[15] = x[0];
        data[16] = x[1];
        data[17] = x[2];

        // YpgSize
        byte[] y = BinaryUtils.convert(height, 3);
        data[18] = y[0];
        data[19] = y[1];
        data[20] = y[2];

        data[21] = 0x00; // Reserved
        data[22] = 0x00; // Reserved
        data[23] = 0x00; // Reserved

        os.write(data);
    }

}

⏎ org/apache/fop/afp/modca/PageDescriptor.java

Or download all of them as a single archive file:

File name: fop-2.7-src.zip
File size: 3401312 bytes
Release date: 2022-01-20
Download 

⇒ "fop" Command in fop-2.7-bin.zip

⇐ What Is fop-2.7-bin.zip

⇑ Download and Installing of FOP 2.x

⇑⇑ FAQ for FOP (Formatting Object Processor)