X-Git-Url: https://git.sesse.net/?p=movit;a=blobdiff_plain;f=dither_effect_test.cpp;fp=dither_effect_test.cpp;h=81f6a2402d6d677e25c2e22727308ead45c491fd;hp=0000000000000000000000000000000000000000;hb=ff9e68a3f5abb179bd7bf9fb84df48327f148583;hpb=3a1e190a989a29edffdfa79bad7994149fc5d27c

diff --git a/dither_effect_test.cpp b/dither_effect_test.cpp
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--- /dev/null
+++ b/dither_effect_test.cpp
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+// Unit tests for DitherEffect.
+
+#include <math.h>
+
+#include "test_util.h"
+#include "gtest/gtest.h"
+
+TEST(DitherEffectTest, NoDitherOnExactValues) {
+	const int size = 4;
+
+	float data[size * size] = {
+		0.0, 1.0, 0.0, 1.0,
+		0.0, 1.0, 1.0, 0.0,
+		0.0, 0.2, 1.0, 0.2,
+		0.0, 0.0, 0.0, 0.0,
+	};
+	unsigned char expected_data[size * size] = {
+		0, 255,   0, 255,
+		0, 255, 255,   0,
+		0,  51, 255,  51,
+		0,   0,   0,   0,
+	};
+	unsigned char out_data[size * size];
+
+	EffectChainTester tester(data, size, size, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR, GL_RGBA8);
+	tester.get_chain()->set_dither_bits(8);
+	tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_LINEAR);
+
+	expect_equal(expected_data, out_data, size, size);
+}
+
+TEST(DitherEffectTest, SinusoidBelowOneLevelComesThrough) {
+	const float frequency = 0.3f * M_PI;
+	const unsigned size = 2048;
+	const float amplitude = 0.25f / 255.0f;  // 6 dB below what can be represented without dithering.
+
+	float data[size];
+	for (unsigned i = 0; i < size; ++i) {
+		data[i] = 0.2 + amplitude * sin(i * frequency);
+	}
+	unsigned char out_data[size];
+
+	EffectChainTester tester(data, size, 1, FORMAT_GRAYSCALE, COLORSPACE_sRGB, GAMMA_LINEAR, GL_RGBA8);
+	tester.get_chain()->set_dither_bits(8);
+	tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_LINEAR);
+
+	// Measure how strong the given sinusoid is in the output.
+	float sum = 0.0f;	
+	for (unsigned i = 0; i < size; ++i) {
+		sum += 2.0 * (int(out_data[i]) - 0.2*255.0) * sin(i * frequency);
+	}
+
+	EXPECT_NEAR(amplitude, sum / (size * 255.0f), 1e-5);
+}