java - 为什么手动压缩PDF中的图像流后图像会失真？

Question

我正在创建一个将图像转换为 PDF 的应用程序。它还具有压缩已创建的 PDF 的功能。这两个功能都在工作。但是在压缩的情况下会出现问题，即PDF文件压缩成功，但压缩后的PDF文件中的大部分图像都变形了。我正在使用 Itext.pdf 库进行转换。我正在粘贴两张图片，第一张图片来自压缩的 PDF，第二张来自压缩的 PDF

我也在粘贴我的代码

// Code for the button, which user Presses to compress a PDF File, I just have chosen a static 
  file for testing here.

   btnCompressPdf.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              try {
                  File mfile;
                  mfile = getFilesDir();
                  farray = mfile.listFiles();
                  PdfReader reader = new PdfReader(new FileInputStream(farray[0]));
                  compressReader(reader);
                  saveReader(reader);
                  reader.close();
              }
              catch(FileNotFoundException ex){

              } catch (DocumentException e) {
                  e.printStackTrace();
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }

      });

下面是我在上面的按钮代码中使用的函数代码

private void compressReader(PdfReader reader) throws IOException {
    int n = reader.getXrefSize();
    PdfObject object;
    PRStream stream;

    for (int i = 0; i < n; i++) {

        object = reader.getPdfObject(i);
        if (object == null || !object.isStream())
            continue;
        stream = (PRStream) object;
        compressStream(stream);
    }

    // code of 'compressStream' function which is called in above function i-e compressReader

   private void compressStream(PRStream stream) throws IOException {
    PdfObject pdfSubType = stream.get(PdfName.SUBTYPE);
    System.out.println(stream.type());
    if (pdfSubType != null && pdfSubType.toString().equals(PdfName.IMAGE.toString())) {
        PdfImageObject image = new PdfImageObject(stream);
        byte[] imageBytes = image.getImageAsBytes();
        Bitmap bmp;

        bmp = BitmapFactory.decodeByteArray(imageBytes, 0, imageBytes.length);
        if (bmp == null) return;

        int width = bmp.getWidth();
        int height = bmp.getHeight();

        Bitmap outBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

        Canvas outCanvas = new Canvas(outBitmap);
        outCanvas.drawBitmap(bmp, 0f, 0f, null);

        ByteArrayOutputStream imgBytes = new ByteArrayOutputStream();

        outBitmap.compress(Bitmap.CompressFormat.JPEG, 100, imgBytes);


        stream.clear();
        stream.setData(imgBytes.toByteArray(), false, PRStream.BEST_COMPRESSION);
        stream.put(PdfName.TYPE, PdfName.XOBJECT);
        stream.put(PdfName.SUBTYPE, PdfName.IMAGE);
        stream.put(PdfName.FILTER, PdfName.DCTDECODE);
        stream.put(PdfName.WIDTH, new PdfNumber(width));
        stream.put(PdfName.HEIGHT, new PdfNumber(height));
        stream.put(PdfName.BITSPERCOMPONENT, new PdfNumber(8));
        stream.put(PdfName.COLORSPACE, PdfName.DEVICERGB);
    }
}
 
  // code for saveReader Function
    
  private void saveReader(PdfReader reader) throws DocumentException, IOException {
    Toast.makeText(MainActivity.this,"inside saveReader",Toast.LENGTH_LONG).show();
    FileOutputStream fileOutputStream = openFileOutput("myFileCompressed"+".pdf", 
    Context.MODE_PRIVATE);

    PdfStamper stamper = new PdfStamper(reader, fileOutputStream);
    stamper.setFullCompression();
    stamper.close();
    Toast.makeText(MainActivity.this,"Pdf Created Successfully",Toast.LENGTH_LONG).show();
}

标签： javaandroidpdfitextdistortion