PdfSizeUtils.java

/*
 * Copyright 2018 Pamarin.com
 */
package com.pamarin.util;

import com.lowagie.text.Document;
import com.lowagie.text.DocumentException;
import com.lowagie.text.PageSize;
import com.lowagie.text.Rectangle;
import com.lowagie.text.pdf.PdfContentByte;
import com.lowagie.text.pdf.PdfImportedPage;
import com.lowagie.text.pdf.PdfReader;
import com.lowagie.text.pdf.PdfWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UncheckedIOException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author jittagornp <http://jittagornp.me> create : 2018/01/26
 */
public class PdfSizeUtils {

    private static final Logger LOG = LoggerFactory.getLogger(PdfSizeUtils.class);

    private static final float A4_WIDTH = PageSize.A4.getWidth();

    private static final float A4_HEIGHT = PageSize.A4.getHeight();

    private PdfSizeUtils() {

    }

    private static boolean isA4(float width, float height) {
        return (width == A4_WIDTH && height == A4_HEIGHT);
    }

    public static boolean isA4(File srcPdf) {
        PdfReader reader = null;
        try (InputStream intputStream = new FileInputStream(srcPdf)) {
            reader = new PdfReader(intputStream);
            Rectangle pageSize = reader.getPageSize(1);//first page
            boolean isA4 = isA4(pageSize.getWidth(), pageSize.getHeight());
            LOG.debug("PDF \"{}\"", srcPdf.getAbsolutePath());
            LOG.debug("Size {}x{} (A4 : {}x{}) is A4 => {}",
                    pageSize.getWidth(),
                    pageSize.getHeight(),
                    A4_WIDTH,
                    A4_HEIGHT,
                    isA4
            );
            return isA4;
        } catch (IOException ex) {
            throw new UncheckedIOException(ex);
        } finally {
            if (reader != null) {
                reader.close();
            }
        }
    }

    public static File convertToA4(File srcPdf, File destFile) {
        try (InputStream intputStream = new FileInputStream(srcPdf);
                OutputStream outputStream = new FileOutputStream(destFile)) {
            PdfReader reader = null;
            PdfWriter writer = null;
            Document document = null;
            try {
                reader = new PdfReader(intputStream);
                document = new Document(new Rectangle(A4_WIDTH, A4_HEIGHT));
                writer = PdfWriter.getInstance(document, outputStream);
                document.open();

                PdfContentByte content = writer.getDirectContent();
                int numberOfPages = reader.getNumberOfPages();
                for (int i = 1; i <= numberOfPages; i++) {
                    PdfImportedPage page = writer.getImportedPage(reader, i);
                    float scale = getA4Scale(page);
                    content.addTemplate(page, scale, 0, 0, scale, 0, 0);
                    document.newPage();
                }

            } finally {
                if (document != null) {
                    document.close();
                }

                if (writer != null) {
                    writer.close();
                }

                if (reader != null) {
                    reader.close();
                }
            }
            return destFile;
        } catch (DocumentException | IOException ex) {
            throw new RuntimeException(ex);
        }
    }

    private static float getA4Scale(PdfImportedPage page) {
        float scaleX = A4_WIDTH / page.getWidth();
        float scaleY = A4_HEIGHT / page.getHeight();
        return Math.min(scaleX, scaleY);
    }
}