什么?发票合并还在开会员？不如看看这个小程序【发票合并】【PDF合并】

/**
     * @Author 小帅丶
     * @Description 普通发票合并成一个PDF
     * @Date  2022年12月27日09:58:59
     * @param pdfParams - PDF数据
     * @param isGray - 是否进行灰度处理图片
     * @param grayType - 灰度类别
     * @return java.io.ByteArrayOutputStream
     **/
    public static ByteArrayOutputStream mergeInvoiceOnePDF(List<PDFParams> pdfParams,
                                                           boolean isGray, Integer grayType) throws Exception {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        if(pdfParams.size()>2){
            throw new Exception("PDF文件个数错误 最多不超过2个");
        }else{
            garyType(grayType);
            //先对PDF进行处理
            List<BufferedImage> allImg = new ArrayList<>();
            long startTime = System.currentTimeMillis();
            for (PDFParams pdfParam : pdfParams) {
                PDFUtils.setFonts(FontFormat.TTF, "STSong-Light", FONT_FILE);
                byte[] bytes = FileUtil.readBytes(pdfParam.getFilePath());
                String pdfBase = Base64Encoder.encode(bytes);
                List<BufferedImage> bufferedImages = PDFUtils.pdfToImage(pdfBase);
                BufferedImage invoiceBI = bufferedImages.get(0);
                if (isGray) {
                    invoiceBI = grayDealImage(invoiceBI, grayType);
                }
                allImg.add(invoiceBI);
            }
            System.out.println("PDF转图片耗时:" + (System.currentTimeMillis() - startTime));
            //开始合并图片到PDF
            if (!allImg.isEmpty()) {
                //合成后的文件
                PdfReader reader = new PdfReader(new FileInputStream(EMPTY_PDF));
                PdfStamper stamper = new PdfStamper(reader, outputStream);
                //将所有图片放在pdf文件的第1页
                PdfContentByte over = stamper.getOverContent(1);
                for (int i = 0; i < allImg.size(); i++) {
                    BufferedImage bufferedImage = allImg.get(i);
                    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
                    ImageIO.write(bufferedImage, "jpg", outStream);
                    //图片转com.itextpdf.text.Image
                    com.itextpdf.text.Image contractSealImg = com.itextpdf.text.Image.getInstance(outStream.toByteArray());
                    over.saveState();
                    PdfGState pdfGState = new PdfGState();
                    //给图片设置透明度
                    pdfGState.setFillOpacity(1F);
                    over.setGState(pdfGState);
                    //缩放比例值
                    double scaleX = (double) DEFAULT_IMG_WIDTH / contractSealImg.getWidth();
                    //计算等比缩放的高度
                    float height = (float) (scaleX * contractSealImg.getHeight());
                    //设置图片位置
                    //PDF从底部左下角算为原点坐标
                    if (i == 0) {
                        contractSealImg.setAbsolutePosition(ABSOLUTE_X, ABSOLUTE_Y);
                    } else {
                        contractSealImg.setAbsolutePosition(ABSOLUTE_X, A4_72_HEIGHT - height);
                    }
                    //设置图片大小
                    contractSealImg.scaleAbsolute(DEFAULT_IMG_WIDTH, height);
                    //将图片添加到pdf文件
                    over.addImage(contractSealImg);
                    over.restoreState();
                    outStream.close();
                }
                stamper.setFormFlattening(true);
                stamper.close();
                reader.close();
                outputStream.close();
            }
            System.out.println("合成总耗时:" + (System.currentTimeMillis() - startTime));
            return outputStream;
        }

    }