From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Sun, 13 Jan 2013 11:50:55 +0000 (+0100)
Subject: Fix alpha handling with sRGB textures.
X-Git-Tag: 1.0~186
X-Git-Url: https://git.sesse.net/?p=movit;a=commitdiff_plain;h=36ae69017f10987948009bf6f602da5f94e4f780

Fix alpha handling with sRGB textures.

OverlayEffect needs working alpha, so this cropped up. We don't
really have full alpha handling everywhere, but this is a good
start; I added some tests here and there to tighten it up a bit.
---

diff --git a/flat_input.cpp b/flat_input.cpp
index 291bb0d..6e118bc 100644
--- a/flat_input.cpp
+++ b/flat_input.cpp
@@ -44,7 +44,7 @@ void FlatInput::finalize()
 		internal_format = GL_RGBA16F_ARB;
 	} else if (output_linear_gamma) {
 		assert(type == GL_UNSIGNED_BYTE);
-		internal_format = GL_SRGB8;
+		internal_format = GL_SRGB8_ALPHA8;
 	} else {
 		assert(type == GL_UNSIGNED_BYTE);
 		internal_format = GL_RGBA8;
diff --git a/flat_input_test.cpp b/flat_input_test.cpp
index 17ee9ce..b717764 100644
--- a/flat_input_test.cpp
+++ b/flat_input_test.cpp
@@ -77,6 +77,37 @@ TEST(FlatInput, RGBA) {
 	expect_equal(expected_data, out_data, 4, size);
 }
 
+// Note: The sRGB conversion itself is tested in EffectChainTester,
+// since it also wants to test the chain building itself.
+// Here, we merely test that alpha is left alone; the test will usually
+// run using the sRGB OpenGL extension, but might be run with a
+// GammaExpansionEffect if the card/driver happens not to support that.
+TEST(FlatInput, AlphaIsNotModifiedBySRGBConversion) {
+	const int size = 5;
+
+	unsigned char data[4 * size] = {
+		0, 0, 0, 0,
+		0, 0, 0, 63,
+		0, 0, 0, 127,
+		0, 0, 0, 191,
+		0, 0, 0, 255,
+	};
+	float expected_data[4 * size] = {
+		0, 0, 0, 0.0 / 255.0,
+		0, 0, 0, 63.0 / 255.0,
+		0, 0, 0, 127.0 / 255.0,
+		0, 0, 0, 191.0 / 255.0,
+		0, 0, 0, 255.0 / 255.0,
+	};
+	float out_data[4 * size];
+
+        EffectChainTester tester(NULL, 1, size);
+        tester.add_input(data, FORMAT_RGBA, COLORSPACE_sRGB, GAMMA_sRGB);
+	tester.run(out_data, GL_RGBA, COLORSPACE_sRGB, GAMMA_LINEAR);
+
+	expect_equal(expected_data, out_data, 4, size);
+}
+
 TEST(FlatInput, BGR) {
 	const int size = 5;
 
diff --git a/gamma_expansion_effect_test.cpp b/gamma_expansion_effect_test.cpp
index ed124c4..71544b4 100644
--- a/gamma_expansion_effect_test.cpp
+++ b/gamma_expansion_effect_test.cpp
@@ -34,6 +34,21 @@ TEST(GammaExpansionEffectTest, sRGB_RampAlwaysIncreases) {
 	}
 }
 
+TEST(GammaExpansionEffectTest, sRGB_AlphaIsUnchanged) {
+	float data[] = {
+		0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.25f,
+		0.0f, 0.0f, 0.0f, 0.5f,
+		0.0f, 0.0f, 0.0f, 0.75f,
+		0.0f, 0.0f, 0.0f, 1.0f,
+	};
+	float out_data[5 * 4];
+	EffectChainTester tester(data, 5, 1, FORMAT_RGBA, COLORSPACE_sRGB, GAMMA_sRGB);
+	tester.run(out_data, GL_RGBA, COLORSPACE_sRGB, GAMMA_LINEAR);
+
+	expect_equal(data, out_data, 5, 1);
+}
+
 TEST(GammaExpansionEffectTest, Rec709_KeyValues) {
 	float data[] = {
 		0.0f, 1.0f,
@@ -63,3 +78,18 @@ TEST(GammaExpansionEffectTest, Rec709_RampAlwaysIncreases) {
 		   << "No increase between " << i-1 << " and " << i;
 	}
 }
+
+TEST(GammaExpansionEffectTest, Rec709_AlphaIsUnchanged) {
+	float data[] = {
+		0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.25f,
+		0.0f, 0.0f, 0.0f, 0.5f,
+		0.0f, 0.0f, 0.0f, 0.75f,
+		0.0f, 0.0f, 0.0f, 1.0f,
+	};
+	float out_data[5 * 4];
+	EffectChainTester tester(data, 5, 1, FORMAT_RGBA, COLORSPACE_sRGB, GAMMA_REC_709);
+	tester.run(out_data, GL_RGBA, COLORSPACE_sRGB, GAMMA_LINEAR);
+
+	expect_equal(data, out_data, 5, 1);
+}