public void merge() throws IOException, Exception
    {
        List<String> tifs = new ArrayList<>(fileList.keySet());
        Collections.sort(tifs);
        for (String key : tifs)
        {
            List<File> files = fileList.get(key);

            // Sorter når der et behov for at listen er sorteret, ikke mens der hentes ud
            Collections.sort(files);
            boolean firstPage = true;
//            TIFFOldJPEGDecompressor tiffReader = new TIFFOldJPEGDecompressor();
//            ImageReader reader = tiffReader
            TIFFImageReaderSpi tiffReader = new TIFFImageReaderSpi();
            ImageReader reader = tiffReader.createReaderInstance();
            TIFFImageWriterSpi tiffWriter = new TIFFImageWriterSpi();
            ImageWriter writer = tiffWriter.createWriterInstance();

//            this.compression = BaselineTIFFTagSet.COMPRESSION_NONE;
//            if (compression == BaselineTIFFTagSet.COMPRESSION_OLD_JPEG)
//            {
//                System.out.println("Old JPEG compressin.");
//            }

//            TIFFOldJPEGDecompressor tiffReader = new TIFFOldJPEGDecompressor();
//            ImageReader reader = tiffReader.createReaderInstance();
//            TIFFImageWriterSpi tiffWriter = new TIFFImageWriterSpi();
//            ImageWriter writer = tiffWriter.createWriterInstance();
//            ImageWriteParam writeParam = writer.getDefaultWriteParam();
            writeParam.setCompressionMode(TIFFImageWriteParam.MODE_EXPLICIT);
//
            writeParam.setTIFFCompressor(compressor);
            writeParam.setCompressionType(compressor.getCompressionType());
//            writeParam.setCompressionQuality(0.5f);

            FileImageOutputStream fileImageOutputStream = new FileImageOutputStream(new File(too.getPath() + "\\" + key + ".tif"));
            writer.setOutput(fileImageOutputStream);
            int pageIndex = 0;
            for (File page : files)
            {
                reader.setInput(new FileImageInputStream(page));
                IIOMetadata metadata = reader.getImageMetadata(0);
                if (firstPage)
                {
                    //Her læse den første side med header.
                    writer.write(null, new IIOImage(reader.readAsRenderedImage(0, null), null, metadata), writeParam);
                    firstPage = false;
                }
                else
                {
                    // Her læser den så de næste sider
                    writer.writeInsert(pageIndex, new IIOImage(reader.readAsRenderedImage(0, null), null, metadata), writeParam);
                }
                pageIndex++;
            }
            writer.dispose();
        }
        JOptionPane.showMessageDialog(rootPane, "Done!");
    }