Default to matrix_coefficients=0 in lossless mode

examples/heif_enc.cc

@@ -168,23 +168,17 @@ void show_help(const char* argv0)
             << "  -e, --encoder ID            select encoder to use (the IDs can be listed with --list-encoders)\n"
             << "      --plugin-directory DIR  load all codec plugins in the directory\n"
             << "  -E, --even-size   [deprecated] crop images to even width and height (odd sizes are not decoded correctly by some software)\n"
-            << "  --matrix_coefficients     nclx profile: color conversion matrix coefficients, default=6 (see h.273)\n"
-            << "  --colour_primaries        nclx profile: color primaries (see h.273)\n"
-            << "  --transfer_characteristic nclx profile: transfer characteristics (see h.273)\n"
+            << "  --colour_primaries        nclx profile: color primaries, default: 1 (see h.273)\n"
+            << "  --transfer_characteristic nclx profile: transfer characteristics, default: 13 (see h.273)\n"
+            << "  --matrix_coefficients     nclx profile: color conversion matrix coefficients, default: 6 for lossy or 0 for lossless (see h.273)\n"
             << "  --full_range_flag         nclx profile: full range flag, default: 1\n"
             << "  --enable-two-colr-boxes   will write both an ICC and an nclx color profile if both are present\n"
             << "  --premultiplied-alpha     input image has premultiplied alpha\n"
             << "  --enable-metadata-compression   enable XMP metadata compression (experimental)\n"
             << "  -C,--chroma-downsampling ALGO   force chroma downsampling algorithm (nn = nearest-neighbor / average / sharp-yuv)\n"
             << "                                  (sharp-yuv makes edges look sharper when using YUV420 with bilinear chroma upsampling)\n"
             << "  --benchmark               measure encoding time, PSNR, and output file size\n"
-            << "  --pitm-description TEXT   (EXPERIMENTAL) set user description for primary image\n"
-
-            << "\n"
-            << "Note: to get lossless encoding, you need this set of options:\n"
-            << "  -L                       switch encoder to lossless mode\n"
-            << "  -p chroma=444            switch off chroma subsampling\n"
-            << "  --matrix_coefficients=0  encode in RGB color-space\n";
+            << "  --pitm-description TEXT   (EXPERIMENTAL) set user description for primary image\n";
 }
 
 
@@ -509,6 +503,7 @@ int main(int argc, char** argv)
         break;
       case 'L':
         lossless = true;
+        nclx_matrix_coefficients = 0;
         break;
       case 'o':
         output_filename = optarg;

libheif/context.cc

@@ -2429,7 +2429,9 @@ 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)
+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,
+                                                                       bool lossless = false)
 {
   auto target_nclx_profile = std::make_shared<color_profile_nclx>();
 
@@ -2446,7 +2448,7 @@ static std::shared_ptr<color_profile_nclx> compute_target_nclx_profile(const std
     target_nclx_profile->set_undefined();
   }
 
-  target_nclx_profile->replace_undefined_values_with_sRGB_defaults();
+  target_nclx_profile->replace_undefined_values_with_sRGB_defaults(lossless);
 
   return target_nclx_profile;
 }
@@ -2466,8 +2468,13 @@ 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();
+  int lossless = 0;
 
-  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile);
+  if (encoder->plugin->supports_lossless_compression) {
+    encoder->plugin->get_parameter_lossless(encoder->encoder, &lossless);
+  }
+
+  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile, static_cast<bool>(lossless));
 
   if (encoder->plugin->plugin_api_version >= 2) {
     encoder->plugin->query_input_colorspace2(encoder->encoder, &colorspace, &chroma);
@@ -2688,8 +2695,13 @@ 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();
+  int lossless = 0;
 
-  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile);
+  if (encoder->plugin->supports_lossless_compression) {
+    encoder->plugin->get_parameter_lossless(encoder->encoder, &lossless);
+  }
+
+  auto target_nclx_profile = compute_target_nclx_profile(image, options.output_nclx_profile, static_cast<bool>(lossless));
 
   if (encoder->plugin->plugin_api_version >= 2) {
     encoder->plugin->query_input_colorspace2(encoder->encoder, &colorspace, &chroma);

libheif/nclx.cc

@@ -343,10 +343,10 @@ void color_profile_nclx::set_from_heif_color_profile_nclx(const struct heif_colo
 }
 
 
-void color_profile_nclx::replace_undefined_values_with_sRGB_defaults()
+void color_profile_nclx::replace_undefined_values_with_sRGB_defaults(bool lossless)
 {
   if (m_matrix_coefficients == heif_matrix_coefficients_unspecified) {
-    m_matrix_coefficients = heif_matrix_coefficients_ITU_R_BT_601_6;
+    m_matrix_coefficients = lossless ? heif_matrix_coefficients_RGB_GBR : heif_matrix_coefficients_ITU_R_BT_601_6;
   }
 
   if (m_colour_primaries == heif_color_primaries_unspecified) {

libheif/nclx.h

@@ -159,7 +159,7 @@ 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_sRGB_defaults();
+  void replace_undefined_values_with_sRGB_defaults(bool lossless=false);
 
 private:
   uint16_t m_colour_primaries = heif_color_primaries_unspecified;

libheif/plugins/encoder_rav1e.cc

@@ -677,7 +677,7 @@ static const struct heif_encoder_plugin encoder_plugin_rav1e
         /* id_name */ "rav1e",
         /* priority */ RAV1E_PLUGIN_PRIORITY,
         /* supports_lossy_compression */ true,
-        /* supports_lossless_compression */ false,
+        /* supports_lossless_compression */ false, // https://github.com/xiph/rav1e/issues/151
         /* get_plugin_name */ rav1e_plugin_name,
         /* init_plugin */ rav1e_init_plugin,
         /* cleanup_plugin */ rav1e_cleanup_plugin,

libheif/plugins/encoder_svt.cc

@@ -859,7 +859,7 @@ static const struct heif_encoder_plugin encoder_plugin_svt
         /* id_name */ "svt",
         /* priority */ SVT_PLUGIN_PRIORITY,
         /* supports_lossy_compression */ true,
-        /* supports_lossless_compression */ false,
+        /* supports_lossless_compression */ false, // https://gitlab.com/AOMediaCodec/SVT-AV1/-/issues/1636
         /* get_plugin_name */ svt_plugin_name,
         /* init_plugin */ svt_init_plugin,
         /* cleanup_plugin */ svt_cleanup_plugin,