+
+/** 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 openjpeg image, which the caller must call opj_image_destroy() on.
+ */
+opj_image_t *
+libdcp::decompress_j2k (uint8_t* data, int64_t size, int reduce)
+{
+ opj_dinfo_t* decoder = opj_create_decompress (CODEC_J2K);
+ 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);
+ opj_image_t* image = opj_decode (decoder, cio);
+ if (!image) {
+ opj_destroy_decompress (decoder);
+ opj_cio_close (cio);
+ boost::throw_exception (DCPReadError ("could not decode JPEG2000 codestream of " + lexical_cast<string> (size) + " bytes."));
+ }
+
+ opj_cio_close (cio);
+
+ image->x1 = rint (float(image->x1) / pow (2, reduce));
+ image->y1 = rint (float(image->y1) / pow (2, reduce));
+ return image;
+}
+
+/** Convert an openjpeg XYZ image to RGB.
+ * @param xyz_frame Frame in XYZ.
+ * @return RGB image.
+ */
+shared_ptr<ARGBFrame>
+libdcp::xyz_to_rgb (opj_image_t* xyz_frame, shared_ptr<const GammaLUT> lut_in, shared_ptr<const GammaLUT> lut_out)
+{
+ float const dci_coefficient = 48.0 / 52.37;
+
+ /* sRGB color matrix for XYZ -> RGB. This is the same as the one used by the Fraunhofer
+ EasyDCP player, I think.
+ */
+
+ float const colour_matrix[3][3] = {
+ { 3.24096989631653, -1.5373831987381, -0.498610764741898 },
+ { -0.96924364566803, 1.87596750259399, 0.0415550582110882 },
+ { 0.0556300804018974, -0.203976958990097, 1.05697154998779 }
+ };
+
+ int const max_colour = pow (2, lut_out->bit_depth()) - 1;
+
+ struct {
+ double x, y, z;
+ } s;
+
+ struct {
+ double r, g, b;
+ } d;
+
+ int* xyz_x = xyz_frame->comps[0].data;
+ int* xyz_y = xyz_frame->comps[1].data;
+ int* xyz_z = xyz_frame->comps[2].data;
+
+ shared_ptr<ARGBFrame> argb_frame (new ARGBFrame (Size (xyz_frame->x1, xyz_frame->y1)));
+
+ uint8_t* argb = argb_frame->data ();
+
+ for (int y = 0; y < xyz_frame->y1; ++y) {
+ uint8_t* argb_line = argb;
+ for (int x = 0; x < xyz_frame->x1; ++x) {
+
+ assert (*xyz_x >= 0 && *xyz_y >= 0 && *xyz_z >= 0 && *xyz_x < 4096 && *xyz_x < 4096 && *xyz_z < 4096);
+
+ /* In gamma LUT */
+ s.x = lut_in->lut()[*xyz_x++];
+ s.y = lut_in->lut()[*xyz_y++];
+ s.z = lut_in->lut()[*xyz_z++];
+
+ /* DCI companding */
+ s.x /= dci_coefficient;
+ s.y /= dci_coefficient;
+ s.z /= dci_coefficient;
+
+ /* XYZ to RGB */
+ d.r = ((s.x * colour_matrix[0][0]) + (s.y * colour_matrix[0][1]) + (s.z * colour_matrix[0][2]));
+ d.g = ((s.x * colour_matrix[1][0]) + (s.y * colour_matrix[1][1]) + (s.z * colour_matrix[1][2]));
+ d.b = ((s.x * colour_matrix[2][0]) + (s.y * colour_matrix[2][1]) + (s.z * colour_matrix[2][2]));
+
+ d.r = min (d.r, 1.0);
+ d.r = max (d.r, 0.0);
+
+ d.g = min (d.g, 1.0);
+ d.g = max (d.g, 0.0);
+
+ d.b = min (d.b, 1.0);
+ d.b = max (d.b, 0.0);
+
+ /* Out gamma LUT */
+ *argb_line++ = lut_out->lut()[(int) (d.b * max_colour)] * 0xff;
+ *argb_line++ = lut_out->lut()[(int) (d.g * max_colour)] * 0xff;
+ *argb_line++ = lut_out->lut()[(int) (d.r * max_colour)] * 0xff;
+ *argb_line++ = 0xff;
+ }