Overwrite an image/pixel data in the dicom file us

I use dcmtk to read a dicom file and extract the image into a .tiff format. After doing some image processing I have an image which I would like to save in the source dicom file.That is overwriting the old image/pixel data with my new ones, while keeping rest of the data(uid,patient name,,etc) same.

I use the following code to read dicom

OFCondition status = src_fileformat.loadFile(src_path);

    if (status.good())
    {
        Sint32 instanceNumber = 0;
        if (src_fileformat.getDataset()->findAndGetSint32(DCM_InstanceNumber, instanceNumber).good())
        {
            cout << "instance Number N: " << instanceNumber << endl;
            sprintf(instanceNum, "%d", instanceNumber);
            printf("%s\n", instanceNum);
        }

        else
            cerr << "Error: cannot access Instance Number!" << endl;
    }
    else
        cerr << "Error: cannot read DICOM file (" << status.text() << ")" << endl;

    src_dcm = new DicomImage(src_path);
    if (src_dcm != NULL)
    {
        if (src_dcm->getStatus() == EIS_Normal)
        {
            if (src_dcm->isMonochrome())
            {
                src_dcm->setMinMaxWindow();
                Uint8 *pixelData = (Uint8 *)(src_dcm->getOutputData(16 /* bits */));
                if (pixelData != NULL)
                {
                    src_dcm->writeBMP("source.tiff", 24);  /* do something useful with the pixel data */
                }
            }
        }
        else
            cerr << "Error: cannot load DICOM image (" << DicomImage::getString(src_dcm->getStatus()) << ")" << endl;
    }

After image processing I have an image that I want to overwrite onto this source dicom file. I looked into image2dcm,but I couldn't get the correct syntax/method to do. any one help me out.. :)

Edit-1

Image2Dcm i2d; 
I2DOutputPlug *outPlug = new I2DOutputPlugSC(); 
 I2DImgSource *inputPlug = new I2DJpegSource(); 
 E_TransferSyntax writeXfer; 
 inputPlug->setImageFile(jpgFile); 
DcmDataset *dataset = NULL; 
OFCondition result = i2d.convert(inputPlug, outPlug, dataset, writeXfer); 

   // Saving output DICOM image 
  if (result.good()) 
      { 
        dataset->putAndInsertString(DCM_PhotometricInterpretation,"RGB"); 

            DcmFileFormat dcmff(dataset); 
    result = dcmff.saveFile(dcmFile, writeXfer); 
       }

I tried the above shown syntax,but couldn't exactly understand it

This is the processed image(above)

This is the original dicom image that I want to overwrite. Guys ,any idea or help??

The basic approach should be:

load the DICOM dataset from file
replace the pixel data in the dataset
modify various other element values (e.g. SOP Instance UID)
save the modified DICOM dataset to a new file

In case of uncompressed images, the second step could be performed in the same manner as the third step, i.e. by an appropriate call of a putAndInsertXXX() method on the dataset. Of course, the element value of the Pixel Data attribute should be in correct DICOM format. See DICOM standard part 3 and 5 for details.