How to get initial JPEG from DICOM?

[ncioj10]

Hi,
I've successfully implemented the conversion of JPEG to DICOM and I want to convert the DICOM back to the same JPEG file, that was sent initially.
However, it seems there is some compression applied when I want to convert it back.
How can I prevent that?
Is it also possible to maintain the EXIF information on the JPEG or otherwise set the image orientation correctly?
I'm sending in Images taken by smartphone, which are already in JPEG.

This is my code:

   DicomImageReader reader = new DicomImageReader(Transcoder.dicomImageReaderSpi);

        BufferedImage myJpegImage;
        DicomImageReadParam param = (DicomImageReadParam)reader.getDefaultReadParam();

        try
        {
            DicomFileInputStream inputStream = new DicomFileInputStream(srcDcm);
            reader.setInput(inputStream,false);
            param.setKeepRgbForLossyJpeg(true);
            myJpegImage = reader.read(0,param);
            inputStream.close();

            if(myJpegImage==null)
            {
                log.error("\nError: Couldn't read dicom image!");
                return;
            }

            File myJpegFile = new File(dstJpg);
            OutputStream output = new BufferedOutputStream( new FileOutputStream(myJpegFile));
            ImageIO.write(myJpegImage, "jpeg", output);
            output.close();
        }
        catch (IOException e)
        {
            log.error("\nError: couldn't read dicom image!"+ e.getMessage());
            return;
        }

Best,
Nico

[nroduit]

If the image is read and re-compressed into jpeg it is normal to lose the metadata and moreover the image will be different because it is recompressed (jpeg is lossy even at 100% quality).

To convert from jpeg to dcm, it is better to use the function of the dicomizer class with the noAPPn parameter set to false (preserves the metadata). Then you just have to extract the jpeg file from the dicom (note that this code must be improved to handle all situations).

If a jpeg has an orientation flag then most dicom viewer will read the image with the orientation according to the data. The dicomization done in Weasis Dicomizer takes this into account and applies the rotation of the data when necessary.

  @Test
  public void dicomize() throws Exception {
    File jpgFile = new File("/home/nicolas/Images/HA3B7268.jpg");
    File dcmFile = new File("/home/nicolas/Images/HA3B7268.dcm");
    Dicomizer.jpeg(new Attributes(), jpgFile, dcmFile, false);
    extractJpeg(dcmFile, new File("/home/nicolas/Images/HA3B7268-2.jpg"));
  }

  public static void extractJpeg(File dicomFile, File outputFile) throws IOException {
    if (dicomFile != null && dicomFile.canRead()) {
      DicomImageReader reader = new DicomImageReader(Transcoder.dicomImageReaderSpi);
      try (DicomFileInputStream inputStream = new DicomFileInputStream(dicomFile.getPath())) {
        reader.setInput(inputStream);
        DicomMetaData dicomMetaData = reader.getStreamMetadata();
        Attributes dcm = dicomMetaData.getDicomObject();
        if(dcm.getInt(Tag.NumberOfFrames, 0) > 1) {
          throw new IllegalStateException("Cannot extract multiframe!");
        }
        VR.Holder pixelatedVR = new VR.Holder();
        Object pixelData = dcm.getValue(Tag.PixelData, pixelatedVR);
        if (pixelData instanceof Fragments) {
          for (Object data : (Fragments) pixelData) {
            if (data instanceof BulkData) {
              BulkData bulkData = (BulkData) data;
              InputStream in = null;
              FileOutputStream out = null;
              try {
                in = new BufferedInputStream(bulkData.openStream());
                out = new FileOutputStream(outputFile);
                StreamUtils.copy(in, out, bulkData.length());
              } catch (Exception e) {
                System.err.println("Cannot extract jpeg stream: " + e.getMessage());
              } finally {
                FileUtil.safeClose(out);
                FileUtil.safeClose(in);
              }
            }
          }
        }
      } finally {
        reader.dispose();
      }
    }
  }

[nroduit]

See examples of orientation flags: https://github.com/recurser/exif-orientation-examples

[ncioj10]

Really thanks a lot for the code it works perfectly.
In our case not necessary, since we are only dealing with images that we loaded into the dicom archive ourselves but for robustness: Would it make sense to also check the TransferSyntax to be JPEG, so we only use this method if we verified that the file contains JPEG?

[nroduit]

Yes you can get it from the dicomMetaData object.