alternative implementation of PR #1015

examples/heif_enc.cc

@@ -64,9 +64,9 @@ int metadata_compression = 0;
 const char* encoderId = nullptr;
 std::string chroma_downsampling;
 
-uint16_t nclx_matrix_coefficients = 6;
-uint16_t nclx_colour_primaries = 2;
-uint16_t nclx_transfer_characteristic = 2;
+uint16_t nclx_matrix_coefficients = 1;
+uint16_t nclx_colour_primaries = 1;
+uint16_t nclx_transfer_characteristic = 13;
 int nclx_full_range = true;
 
 std::string property_pitm_description;

libheif/color-conversion/colorconversion.cc

@@ -520,19 +520,7 @@ std::shared_ptr<HeifPixelImage> convert_colorspace(const std::shared_ptr<HeifPix
     input_state.nclx_profile = *input->get_color_profile_nclx();
   }
 
-  // If some input nclx values are unspecified, use values that match sRGB as default.
-
-  if (input_state.nclx_profile.get_matrix_coefficients() == heif_matrix_coefficients_unspecified) {
-    input_state.nclx_profile.set_matrix_coefficients(heif_matrix_coefficients_ITU_R_BT_709_5);
-  }
-
-  if (input_state.nclx_profile.get_colour_primaries() == heif_color_primaries_unspecified) {
-    input_state.nclx_profile.set_colour_primaries(heif_color_primaries_ITU_R_BT_709_5);
-  }
-
-  if (input_state.nclx_profile.get_transfer_characteristics() == heif_transfer_characteristic_unspecified) {
-    input_state.nclx_profile.set_transfer_characteristics(heif_transfer_characteristic_IEC_61966_2_1);
-  }
+  input_state.nclx_profile.replace_undefined_values_with_defaults();
 
   std::set<enum heif_channel> channels = input->get_channel_set();
   assert(!channels.empty());

libheif/context.cc

@@ -2429,6 +2429,29 @@ static bool nclx_profile_matches_spec(heif_colorspace colorspace,
 }
 
 
+static std::shared_ptr<color_profile_nclx> compute_target_nclx_profile(const std::shared_ptr<HeifPixelImage>& image, const heif_color_profile_nclx* output_nclx_profile)
+{
+  auto target_nclx_profile = std::make_shared<color_profile_nclx>();
+
+  // If there is an output NCLX specified, use that.
+  if (output_nclx_profile) {
+    target_nclx_profile->set_from_heif_color_profile_nclx(output_nclx_profile);
+  }
+  // Otherwise, if there is an input NCLX, keep that.
+  else if (auto input_nclx = image->get_color_profile_nclx()) {
+    *target_nclx_profile = *input_nclx;
+  }
+  // Otherwise, just use the defaults (set below)
+  else {
+    target_nclx_profile->set_undefined();
+  }
+
+  target_nclx_profile->replace_undefined_values_with_defaults();
+
+  return target_nclx_profile;
+}
+
+
 Error HeifContext::encode_image_as_hevc(const std::shared_ptr<HeifPixelImage>& image,
                                         struct heif_encoder* encoder,
                                         const struct heif_encoding_options& options,
@@ -2444,8 +2467,7 @@ Error HeifContext::encode_image_as_hevc(const std::shared_ptr<HeifPixelImage>& i
   heif_colorspace colorspace = image->get_colorspace();
   heif_chroma chroma = image->get_chroma_format();
 
-  auto target_nclx_profile = std::make_shared<color_profile_nclx>();
-  target_nclx_profile->set_from_heif_color_profile_nclx(options.output_nclx_profile);
+  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile);
 
   if (encoder->plugin->plugin_api_version >= 2) {
     encoder->plugin->query_input_colorspace2(encoder->encoder, &colorspace, &chroma);
@@ -2652,8 +2674,7 @@ Error HeifContext::encode_image_as_av1(const std::shared_ptr<HeifPixelImage>& im
   heif_colorspace colorspace = image->get_colorspace();
   heif_chroma chroma = image->get_chroma_format();
 
-  auto target_nclx_profile = std::make_shared<color_profile_nclx>();
-  target_nclx_profile->set_from_heif_color_profile_nclx(options.output_nclx_profile);
+  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile);
 
   if (encoder->plugin->plugin_api_version >= 2) {
     encoder->plugin->query_input_colorspace2(encoder->encoder, &colorspace, &chroma);
@@ -2828,8 +2849,7 @@ Error HeifContext::encode_image_as_jpeg2000(const std::shared_ptr<HeifPixelImage
   auto nclx_profile = std::dynamic_pointer_cast<const color_profile_nclx>(color_profile);
 */
 
-  auto target_nclx_profile = std::make_shared<color_profile_nclx>();
-  target_nclx_profile->set_from_heif_color_profile_nclx(options.output_nclx_profile);
+  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile);
 
   if (encoder->plugin->plugin_api_version >= 2) {
     encoder->plugin->query_input_colorspace2(encoder->encoder, &colorspace, &chroma);

libheif/nclx.cc

@@ -339,6 +339,22 @@ void color_profile_nclx::set_from_heif_color_profile_nclx(const struct heif_colo
 }
 
 
+void color_profile_nclx::replace_undefined_values_with_defaults()
+{
+  if (m_matrix_coefficients == heif_matrix_coefficients_unspecified) {
+    m_matrix_coefficients = heif_matrix_coefficients_ITU_R_BT_709_5;
+  }
+
+  if (m_colour_primaries == heif_color_primaries_unspecified) {
+    m_colour_primaries = heif_color_primaries_ITU_R_BT_709_5;
+  }
+
+  if (m_transfer_characteristics == heif_color_primaries_unspecified) {
+    m_transfer_characteristics = heif_transfer_characteristic_IEC_61966_2_1;
+  }
+}
+
+
 Error Box_colr::parse(BitstreamRange& range)
 {
   StreamReader::grow_status status;

libheif/nclx.h

@@ -159,6 +159,8 @@ class color_profile_nclx : public color_profile
 
   void set_from_heif_color_profile_nclx(const struct heif_color_profile_nclx* nclx);
 
+  void replace_undefined_values_with_defaults();
+
 private:
   uint16_t m_colour_primaries = heif_color_primaries_unspecified;
   uint16_t m_transfer_characteristics = heif_transfer_characteristic_unspecified;