colorspace: add ST.428-1 (gamma 2.6) transfer function

sekrit-twc · Jun 30, 2023 · f80b515 · f80b515
1 parent 3d83f6a
commit f80b515
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Showing 8 changed files with 28 additions and 4 deletions.
diff --git a/src/testapp/table.cpp b/src/testapp/table.cpp
@@ -81,7 +81,7 @@ const zimg::static_string_map<MatrixCoefficients, 12> g_matrix_table{
 	{ "ictcp",      MatrixCoefficients::REC_2100_ICTCP },
 };
 
-const zimg::static_string_map<TransferCharacteristics, 12> g_transfer_table{
+const zimg::static_string_map<TransferCharacteristics, 13> g_transfer_table{
 	{ "unspec",   TransferCharacteristics::UNSPECIFIED },
 	{ "linear",   TransferCharacteristics::LINEAR },
 	{ "log100",   TransferCharacteristics::LOG_100 },
@@ -93,6 +93,7 @@ const zimg::static_string_map<TransferCharacteristics, 12> g_transfer_table{
 	{ "xvycc",    TransferCharacteristics::XVYCC },
 	{ "srgb",     TransferCharacteristics::SRGB },
 	{ "st_2084",  TransferCharacteristics::ST_2084 },
+	{ "st_428",   TransferCharacteristics::ST_428 },
 	{ "arib_b67", TransferCharacteristics::ARIB_B67 },
 };
 

diff --git a/src/testapp/table.h b/src/testapp/table.h
@@ -37,7 +37,7 @@ class Filter;
 extern const zimg::static_string_map<zimg::CPUClass, 9> g_cpu_table;
 extern const zimg::static_string_map<zimg::PixelType, 4> g_pixel_table;
 extern const zimg::static_string_map<zimg::colorspace::MatrixCoefficients, 12> g_matrix_table;
-extern const zimg::static_string_map<zimg::colorspace::TransferCharacteristics, 12> g_transfer_table;
+extern const zimg::static_string_map<zimg::colorspace::TransferCharacteristics, 13> g_transfer_table;
 extern const zimg::static_string_map<zimg::colorspace::ColorPrimaries, 12> g_primaries_table;
 extern const zimg::static_string_map<zimg::depth::DitherType, 4> g_dither_table;
 extern const zimg::static_string_map<std::unique_ptr<zimg::resize::Filter>(*)(double, double), 8> g_resize_table;

diff --git a/src/zimg/api/zimg.cpp b/src/zimg/api/zimg.cpp
@@ -266,7 +266,7 @@ zimg::colorspace::TransferCharacteristics translate_transfer(zimg_transfer_chara
 {
 	using zimg::colorspace::TransferCharacteristics;
 
-	static SM_CONSTEXPR_14 const zimg::static_map<zimg_transfer_characteristics_e, TransferCharacteristics, 15> map{
+	static SM_CONSTEXPR_14 const zimg::static_map<zimg_transfer_characteristics_e, TransferCharacteristics, 16> map{
 		{ ZIMG_TRANSFER_BT709,         TransferCharacteristics::REC_709 },
 		{ ZIMG_TRANSFER_UNSPECIFIED,   TransferCharacteristics::UNSPECIFIED },
 		{ ZIMG_TRANSFER_ST240_M,       TransferCharacteristics::SMPTE_240M },
@@ -281,6 +281,7 @@ zimg::colorspace::TransferCharacteristics translate_transfer(zimg_transfer_chara
 		{ ZIMG_TRANSFER_LOG_100,       TransferCharacteristics::LOG_100 },
 		{ ZIMG_TRANSFER_LOG_316,       TransferCharacteristics::LOG_316 },
 		{ ZIMG_TRANSFER_ST2084,        TransferCharacteristics::ST_2084 },
+		{ ZIMG_TRANSFER_ST428,         TransferCharacteristics::ST_428 },
 		{ ZIMG_TRANSFER_ARIB_B67,      TransferCharacteristics::ARIB_B67 },
 	};
 	return search_itu_enum_map(map, transfer, "unrecognized transfer characteristics");

diff --git a/src/zimg/api/zimg.h b/src/zimg/api/zimg.h
@@ -315,6 +315,7 @@ typedef enum zimg_transfer_characteristics_e {
 	ZIMG_TRANSFER_BT2020_10     = 14, /* Equivalent to 1. */
 	ZIMG_TRANSFER_BT2020_12     = 15, /* Equivalent to 1. */
 	ZIMG_TRANSFER_ST2084        = 16,
+	ZIMG_TRANSFER_ST428         = 17,
 	ZIMG_TRANSFER_ARIB_B67      = 18
 #define ZIMG_TRANSFER_709     ZIMG_TRANSFER_BT709     /**< Deprecated. */
 #define ZIMG_TRANSFER_470_M   ZIMG_TRANSFER_BT470_M   /**< Deprecated. */

diff --git a/src/zimg/colorspace/colorspace.h b/src/zimg/colorspace/colorspace.h
@@ -46,6 +46,7 @@ enum class TransferCharacteristics {
 	XVYCC,
 	SRGB,
 	ST_2084,
+	ST_428,
 	ARIB_B67,
 };
 

diff --git a/src/zimg/colorspace/gamma.cpp b/src/zimg/colorspace/gamma.cpp
@@ -275,6 +275,16 @@ float st_2084_inverse_eotf(float x) noexcept
 	return x;
 }
 
+float st_428_eotf(float x) noexcept
+{
+	return x < 0.0f ? 0.0f : zimg_x_powf(x, 2.6f);
+}
+
+float st_428_inverse_eotf(float x) noexcept
+{
+	return x < 0.0f ? 0.0f : zimg_x_powf(x, 1.0f / 2.6f);
+}
+
 // Applies a per-channel correction instead of the iterative method specified in Rec.2100.
 float arib_b67_eotf(float x) noexcept
 {
@@ -345,6 +355,10 @@ TransferFunction select_transfer_function(TransferCharacteristics transfer, doub
 		func.to_linear_scale = static_cast<float>(ST2084_PEAK_LUMINANCE / peak_luminance);
 		func.to_gamma_scale = static_cast<float>(peak_luminance / ST2084_PEAK_LUMINANCE);
 		break;
+	case TransferCharacteristics::ST_428:
+		func.to_linear = st_428_eotf;
+		func.to_gamma = st_428_inverse_eotf;
+		break;
 	case TransferCharacteristics::ARIB_B67:
 		func.to_linear = scene_referred ? arib_b67_inverse_oetf : arib_b67_eotf;
 		func.to_gamma = scene_referred ? arib_b67_oetf : arib_b67_inverse_eotf;

diff --git a/src/zimg/colorspace/gamma.h b/src/zimg/colorspace/gamma.h
@@ -50,6 +50,9 @@ float srgb_inverse_eotf(float x) noexcept;
 float st_2084_eotf(float x) noexcept;
 float st_2084_inverse_eotf(float x) noexcept;
 
+float st_428_eotf(float x) noexcept;
+float st_428_inverse_eotf(float x) noexcept;
+
 // Derived functions.
 float arib_b67_eotf(float x) noexcept;
 float arib_b67_inverse_eotf(float x) noexcept;

diff --git a/test/colorspace/gamma_test.cpp b/test/colorspace/gamma_test.cpp
@@ -118,14 +118,17 @@ TEST(GammaTest, test_log316)
 	test_monotonic(zimg::colorspace::log316_oetf, 1.0f, 2.0f, 1UL << 16);
 }
 
-TEST(GammaTest, test_rec_470m_470bg)
+TEST(GammaTest, test_rec_470m_470bg_st428)
 {
 	SCOPED_TRACE("470m");
 	test_accuracy(zimg::colorspace::rec_470m_oetf, zimg::colorspace::rec_470m_inverse_oetf, 0.0f, 1.0f, 1e-6f, 1e-6f);
 	test_accuracy(zimg::colorspace::rec_470m_inverse_oetf, zimg::colorspace::rec_470m_oetf, 0.0f, 1.0f, 1e-6f, 1e-6f);
 	SCOPED_TRACE("470bg");
 	test_accuracy(zimg::colorspace::rec_470bg_oetf, zimg::colorspace::rec_470bg_inverse_oetf, 0.0f, 1.0f, 1e-6f, 1e-6f);
 	test_accuracy(zimg::colorspace::rec_470bg_inverse_oetf, zimg::colorspace::rec_470bg_oetf, 0.0f, 1.0f, 1e-6f, 1e-6f);
+	SCOPED_TRACE("st428");
+	test_accuracy(zimg::colorspace::st_428_eotf, zimg::colorspace::st_428_inverse_eotf, 0.0f, 1.0f, 1e-6f, 1e-6f);
+	test_accuracy(zimg::colorspace::st_428_inverse_eotf, zimg::colorspace::st_428_eotf, 0.0f, 1.0f, 1e-6f, 1e-6f);
 }
 
 TEST(GammaTest, test_smpte_240m)
-Original file line number
+Diff line change
@@ Expand Up / @@ -46,6 +46,7 @@ enum class TransferCharacteristics { @@
     	XVYCC,
     	SRGB,
     	ST_2084,
+    	ST_428,
     	ARIB_B67,
     };
@@ Expand Down @@