//
// 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 <math.h>
#include <GL/glew.h>
#include "gtest/gtest.h"
#include "image_format.h"
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) {
}
}
+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,
}
}
+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[256];
- for (unsigned i = 0; i < 256; ++i) {
- data[i] = i / 255.0f;
+ float data[4096];
+ for (unsigned i = 0; i < 4096; ++i) {
+ data[i] = i / 4095.0f;
}
- float out_data_709[256];
- float out_data_2020[256];
+ float out_data_709[4096];
+ float out_data_2020[4096];
- EffectChainTester tester(data, 256, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR);
+ 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, 256, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR);
+ 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 < 256; ++i) {
- EXPECT_NEAR(out_data_709[i], out_data_2020[i], 1e-3);
+ 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);
+}
projects / movit / blobdiff