-/** Decompress a JPEG2000 image to a bitmap.
- * @param data JPEG2000 data.
- * @param size Size of data in bytes.
- * @param reduce A power of 2 by which to reduce the size of the decoded image;
- * e.g. 0 reduces by (2^0 == 1), ie keeping the same size.
- * 1 reduces by (2^1 == 2), ie halving the size of the image.
- * This is useful for scaling 4K DCP images down to 2K.
- * @return OpenJPEGImage.
- */
-shared_ptr<dcp::OpenJPEGImage>
-dcp::decompress_j2k (uint8_t* data, int64_t size, int reduce)
-{
- uint8_t const jp2_magic[] = {
- 0x00,
- 0x00,
- 0x00,
- 0x0c,
- 'j',
- 'P',
- 0x20,
- 0x20
- };
-
- OPJ_CODEC_FORMAT format = CODEC_J2K;
- if (size >= int (sizeof (jp2_magic)) && memcmp (data, jp2_magic, sizeof (jp2_magic)) == 0) {
- format = CODEC_JP2;
- }
-
- opj_dinfo_t* decoder = opj_create_decompress (format);
- if (!decoder) {
- boost::throw_exception (DCPReadError ("could not create JPEG2000 decompresser"));
- }
- opj_dparameters_t parameters;
- opj_set_default_decoder_parameters (¶meters);
- parameters.cp_reduce = reduce;
- opj_setup_decoder (decoder, ¶meters);
- opj_cio_t* cio = opj_cio_open ((opj_common_ptr) decoder, data, size);
- if (!cio) {
- boost::throw_exception (DCPReadError ("could not create JPEG2000 memory stream"));
- }
- opj_image_t* image = opj_decode (decoder, cio);
- if (!image) {
- opj_destroy_decompress (decoder);
- opj_cio_close (cio);
- if (format == CODEC_J2K) {
- boost::throw_exception (DCPReadError (String::compose ("could not decode JPEG2000 codestream of %1 bytes.", size)));
- } else {
- boost::throw_exception (DCPReadError (String::compose ("could not decode JP2 file of %1 bytes.", size)));
- }
- }
-
- opj_destroy_decompress (decoder);
- opj_cio_close (cio);
-
- image->x1 = rint (float(image->x1) / pow (2, reduce));
- image->y1 = rint (float(image->y1) / pow (2, reduce));
- return shared_ptr<OpenJPEGImage> (new OpenJPEGImage (image));
-}
-