import com.itextpdf.text.Element;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.BaseFont;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfGState;
import com.itextpdf.text.pdf.PdfReader;
import com.itextpdf.text.pdf.PdfStamper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ClassUtils;

import javax.swing.*;
import java.awt.*;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.util.Objects;

/**
 * @author zly
 * @since 2020/8/13 16:46
 */
public class PdfAddWatermark {
    private final static Logger logger = LoggerFactory.getLogger(PdfAddWatermark.class);

    /**
     * 字体路径
     * private static final String TTF_PAHT = "TTF文件路径";
     */
    private static final String TTF_PATH = Objects.requireNonNull(ClassUtils.getDefaultClassLoader().getResource("")).getPath() + "static/files/ttf";

    /**
     * 添加水印
     * 备注：
     * 在内容下方加水印
     * content = stamper.getUnderContent(i);
     * 间隔
     * int interval = -5;
     * 根据纸张大小多次添加， 水印文字成30度角倾斜
     * for (int height = interval + textH; height < pageHeight; height = height + textH * 3) {
     * for (int width = interval + textW; width < pageWidth + textW; width = width + textW * 2) {
     * content.showTextAligned(Element.ALIGN_LEFT, waterMarkName, width - textW, height - textH, 30);
     * }
     * }
     *
     * @param pdfPathAndName        原pdf位置
     * @param waterMarkName         水印内容
     * @param fileOutPutPathAndName 输出路径
     */
    public static String pdfAddWatermark(String pdfPathAndName, String waterMarkName, String fileOutPutPathAndName) {
        logger.info("-----------------------------pdf添加水印--------------------------------------");
        long start = System.currentTimeMillis();
        PdfReader reader = null;
        PdfStamper stamper = null;
        try {
            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(new File(fileOutPutPathAndName)));
            reader = new PdfReader(pdfPathAndName);
            stamper = new PdfStamper(reader, bos);
            // 获取总页数 +1, 下面从1开始遍历
            int total = reader.getNumberOfPages() + 1;
            // 使用classpath下面的字体库
            BaseFont base = BaseFont.createFont(TTF_PATH + "/SIMYOU.TTF", BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);

            // 获取水印文字的高度和宽度
            JLabel label = new JLabel();
            label.setText(waterMarkName);
            FontMetrics metrics = label.getFontMetrics(label.getFont());
            // 文字高度
            metrics.getHeight();
            // 文字宽度
            metrics.stringWidth(label.getText());

            // 设置水印透明度
            PdfGState gs = new PdfGState();
            gs.setFillOpacity(0.4f);
            gs.setStrokeOpacity(0.4f);

            Rectangle pageSizeWithRotation;
            PdfContentByte content;
            for (int i = 1; i < total; i++) {
                // 在内容上方加水印
                content = stamper.getOverContent(i);
                content.saveState();
                content.setGState(gs);

                // 设置字体和字体大小
                content.beginText();
                content.setFontAndSize(base, 100);

                // 获取每一页的高度、宽度
                pageSizeWithRotation = reader.getPageSizeWithRotation(i);
                float pageHeight = pageSizeWithRotation.getHeight();
                float pageWidth = pageSizeWithRotation.getWidth();
                content.showTextAligned(Element.ALIGN_LEFT, waterMarkName, pageWidth / 2 - 100, pageHeight / 2 - 100, 30);
                content.endText();
            }
            long end = System.currentTimeMillis();
            logger.info("------------------------pdf添加水印完成，用时：" + (end - start) + "ms--------------------------");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (stamper != null) {
                    stamper.close();
                    logger.info("-------------------------------------流关闭-------------------------------------------");
                }
            } catch (Exception e) {
                logger.error("----------------------pdf添加水印失败,异常信息:" + e.getMessage() + "--------------------------");
            }
            try {
                if (reader != null) {
                    reader.close();
                    logger.info("-------------------------------------流关闭-------------------------------------------");
                }
            } catch (Exception e) {
                logger.error("----------------------pdf添加水印失败,异常信息:" + e.getMessage() + "--------------------------");
            }
        }
        return fileOutPutPathAndName;
    }
}