X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=gamma_compression_effect_test.cpp;h=465d23948cd623808b20af119839959893fb7800;hp=c0b4ccf141e1d58a2d456b03acedae725ac42399;hb=85f9719bf3519b1f1942738d11601584f5d38725;hpb=37f56fcbe571b2322243f6de59494bf9e0cbb37a diff --git a/gamma_compression_effect_test.cpp b/gamma_compression_effect_test.cpp index c0b4ccf..465d239 100644 --- a/gamma_compression_effect_test.cpp +++ b/gamma_compression_effect_test.cpp @@ -2,7 +2,10 @@ // // Pretty much the inverse of the GammaExpansionEffect tests; // EffectChainTest tests that they are actually inverses. +// However, the accuracy tests are somewhat simpler, since we +// only need to care about absolute errors and not relative. +#include #include #include "gtest/gtest.h" #include "image_format.h" @@ -12,16 +15,18 @@ TEST(GammaCompressionEffectTest, sRGB_KeyValues) { float data[] = { 0.0f, 1.0f, 0.00309f, 0.00317f, // On either side of the discontinuity. + -0.5f, 1.5f, // To check clamping. }; float expected_data[] = { 0.0f, 1.0f, 0.040f, 0.041f, + 0.0f, 1.0f, }; float out_data[4]; - EffectChainTester tester(data, 2, 2, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR); + EffectChainTester tester(data, 2, 3, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR); tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_sRGB); - expect_equal(expected_data, out_data, 2, 2); + expect_equal(expected_data, out_data, 2, 3); } TEST(GammaCompressionEffectTest, sRGB_RampAlwaysIncreases) { @@ -38,6 +43,33 @@ TEST(GammaCompressionEffectTest, sRGB_RampAlwaysIncreases) { } } +TEST(GammaCompressionEffectTest, sRGB_Accuracy) { + float data[256], expected_data[256], out_data[256]; + + for (int i = 0; i < 256; ++i) { + double x = i / 255.0; + + expected_data[i] = x; + + // From the Wikipedia article on sRGB. + if (x < 0.04045) { + data[i] = x / 12.92; + } else { + data[i] = pow((x + 0.055) / 1.055, 2.4); + } + } + + EffectChainTester tester(data, 256, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR, GL_RGBA32F); + tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_sRGB); + + // Maximum absolute error is 25% of one pixel level. For comparison, + // a straightforward ALU solution (using a branch and pow()), used as a + // “high anchor” to indicate limitations of float arithmetic etc., + // reaches maximum absolute error of 3.7% of one pixel level + // and rms of 3.2e-6. + expect_equal(expected_data, out_data, 256, 1, 0.25 / 255.0, 1e-4); +} + TEST(GammaCompressionEffectTest, Rec709_KeyValues) { float data[] = { 0.0f, 1.0f, @@ -67,3 +99,114 @@ TEST(GammaCompressionEffectTest, Rec709_RampAlwaysIncreases) { << "No increase between " << i-1 << " and " << i; } } + +TEST(GammaCompressionEffectTest, Rec709_Accuracy) { + float data[256], expected_data[256], out_data[256]; + + for (int i = 0; i < 256; ++i) { + double x = i / 255.0; + + expected_data[i] = x; + + // Rec. 2020, page 3. + if (x < 0.018 * 4.5) { + data[i] = x / 4.5; + } else { + data[i] = pow((x + 0.099) / 1.099, 1.0 / 0.45); + } + } + + EffectChainTester tester(data, 256, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR, GL_RGBA32F); + tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_REC_709); + + // Maximum absolute error is 25% of one pixel level. For comparison, + // a straightforward ALU solution (using a branch and pow()), used as a + // “high anchor” to indicate limitations of float arithmetic etc., + // reaches maximum absolute error of 3.7% of one pixel level + // and rms of 3.5e-6. + expect_equal(expected_data, out_data, 256, 1, 0.25 / 255.0, 1e-5); +} + +// This test tests the same gamma ramp as Rec709_Accuracy, but with 10-bit +// input range and somewhat looser error bounds. (One could claim that this is +// already on the limit of what we can reasonably do with fp16 input, if you +// look at the local relative error.) +TEST(GammaCompressionEffectTest, Rec2020_10Bit_Accuracy) { + float data[1024], expected_data[1024], out_data[1024]; + + for (int i = 0; i < 1024; ++i) { + double x = i / 1023.0; + + expected_data[i] = x; + + // Rec. 2020, page 3. + if (x < 0.018 * 4.5) { + data[i] = x / 4.5; + } else { + data[i] = pow((x + 0.099) / 1.099, 1.0 / 0.45); + } + } + + EffectChainTester tester(data, 1024, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR, GL_RGBA32F); + tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_REC_2020_10_BIT); + + // Maximum absolute error is 30% of one pixel level. For comparison, + // a straightforward ALU solution (using a branch and pow()), used as a + // “high anchor” to indicate limitations of float arithmetic etc., + // reaches maximum absolute error of 25.2% of one pixel level + // and rms of 1.8e-6, so this is probably mostly related to input precision. + expect_equal(expected_data, out_data, 1024, 1, 0.30 / 1023.0, 1e-5); +} + +TEST(GammaCompressionEffectTest, Rec2020_12BitIsVeryCloseToRec709) { + float data[4096]; + for (unsigned i = 0; i < 4096; ++i) { + data[i] = i / 4095.0f; + } + float out_data_709[4096]; + float out_data_2020[4096]; + + EffectChainTester tester(data, 4096, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR); + tester.run(out_data_709, GL_RED, COLORSPACE_sRGB, GAMMA_REC_709); + EffectChainTester tester2(data, 4096, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR); + tester2.run(out_data_2020, GL_RED, COLORSPACE_sRGB, GAMMA_REC_2020_12_BIT); + + double sqdiff = 0.0; + for (unsigned i = 0; i < 4096; ++i) { + EXPECT_NEAR(out_data_709[i], out_data_2020[i], 0.001); + sqdiff += (out_data_709[i] - out_data_2020[i]) * (out_data_709[i] - out_data_2020[i]); + } + EXPECT_GT(sqdiff, 1e-6); +} + +// The fp16 _input_ provided by FlatInput is not enough to distinguish between +// all of the possible 12-bit input values (every other level translates to the +// same value). Thus, this test has extremely loose bounds; if we ever decide +// to start supporting fp32, we should re-run this and tighten them a lot. +TEST(GammaCompressionEffectTest, Rec2020_12Bit_Inaccuracy) { + float data[4096], expected_data[4096], out_data[4096]; + + for (int i = 0; i < 4096; ++i) { + double x = i / 4095.0; + + expected_data[i] = x; + + // Rec. 2020, page 3. + if (x < 0.0181 * 4.5) { + data[i] = x / 4.5; + } else { + data[i] = pow((x + 0.0993) / 1.0993, 1.0 / 0.45); + } + } + + EffectChainTester tester(data, 4096, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR, GL_RGBA32F); + tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_REC_2020_12_BIT); + + // Maximum absolute error is 120% of one pixel level. For comparison, + // a straightforward ALU solution (using a branch and pow()), used as a + // “high anchor” to indicate limitations of float arithmetic etc., + // reaches maximum absolute error of 71.1% of one pixel level + // and rms of 0.9e-6, so this is probably a combination of input + // precision and inaccuracies in the polynomial approximation. + expect_equal(expected_data, out_data, 4096, 1, 1.2 / 4095.0, 1e-5); +}