Method decode

multiresolutionimageinterface/JPEG2000Codec.cpp:159–219

}

void JPEG2000Codec::decode(unsigned char* buf, const unsigned int& inSize, const unsigned int& outSize)
{
  opj_memory_stream decodeStream;
  // OpenJPEG stuff.
  opj_image_t		*decompImage = NULL;
  opj_stream_t		*l_stream = NULL;

  //Set up the input buffer as a stream
  decodeStream.data = (OPJ_UINT8 *)buf;
  decodeStream.size = inSize;
  decodeStream.offset = 0;
    //Open the memory as a stream.
  l_stream = opj_stream_create_default_memory_stream(&decodeStream, OPJ_TRUE);

  opj_dparameters_t decodeParameters;
  opj_set_default_decoder_parameters(&decodeParameters);
  opj_codec_t* decoder = opj_create_decompress(OPJ_CODEC_FORMAT::OPJ_CODEC_J2K);//Bad openjpeg, can't be reused!
  //Catch events using our callbacks and give a local context.
  opj_set_info_handler(decoder, info_callback, NULL);
  opj_set_warning_handler(decoder, warning_callback, NULL);
  opj_set_error_handler(decoder, error_callback, NULL);

  //Setup the decoder decoding parameters using user parameters.
  opj_setup_decoder(decoder, &decodeParameters);
#if OPJ_VERSION_MAJOR >= 2 && OPJ_VERSION_MINOR >= 3
  opj_codec_set_threads(decoder, 4);
#endif

  // Read the main header of the codestream, if necessary the JP2 boxes, and create decompImage.
  OPJ_BOOL headerSucces = opj_read_header(l_stream, decoder, &decompImage);
  OPJ_BOOL setAreaSucces = opj_set_decode_area(decoder, decompImage, decodeParameters.DA_x0,
      decodeParameters.DA_y0, decodeParameters.DA_x1, decodeParameters.DA_y1);
  OPJ_BOOL decodeSucces = opj_decode(decoder, l_stream, decompImage);
  OPJ_BOOL decompressSuccess = opj_end_decompress(decoder, l_stream);
  
  //Done with the input stream and the decoder.
  opj_stream_destroy(l_stream);
  opj_destroy_codec(decoder);

  //Get the total uncompressed length.
  int prec_jpc = decompImage->comps[0].prec; //Need it at the end
  int bytes_jpc= (prec_jpc + 7) / 8;// Bytes or words.
  int stream_len = (decompImage->comps[0].w * decompImage->comps[0].h);

  OPJ_INT32 ** compPointers = new OPJ_INT32*[decompImage->numcomps];
  for (unsigned int cmp = 0; cmp < decompImage->numcomps; cmp++) {
    compPointers[cmp] = decompImage->comps[cmp].data;
  }
  std::fill(buf, buf + outSize, 0);
  for (int index = 0; index < stream_len; index++) {
    for (unsigned int cmp = 0; cmp < decompImage->numcomps; cmp++) {
      for (int byteCnt = 0; byteCnt < bytes_jpc; byteCnt++)
      {
        *(buf)++ |= (unsigned char)((*compPointers[cmp] >> (8 * byteCnt)) & 0xFF);
      }
      *compPointers[cmp]++;
    }
  }