Fix the order of applying layer alpha and color matrices in GLESRenderEngine
If the system want to do a color inversion,
there is an unexpected result due to applying the layer alpha first.
Solution: RenderEngine should apply
the layer's alpha after multiplying by the color matrix.
For example, given the following color inversion matrix:
| r.r r.g r.b | | -1.0 0.0 0.0 |
| g.r g.g g.b | = | 0.0 -1.0 0.0 |
| b.r b.g b.b | | 0.0 0.0 -1.0 |
| Tr Tg Tb | | 1.0 1.0 1.0 |
We want to get a black layer when applying the color transform to a white layer;
However, the white layer applies layer alpha before color matrix. We can get
the below calculation: When layer alpha is 0, R_out value was always Tr.
Then we do not get a black layer when the system applies color inversion to a
white layer.
R_out = (R_in * layer_alpha) * r.r + Tr
Therefore we apply the color matrix first, so we can get the below calculation.
When the layer alpha is 0, we can get a black layer.
R_out = (R_in * r.r + Tr) * layer_alpha
= (R_in * r.r * layer_alpha) + (Tr * layer_alpha)
adds RenderEngineTest::fillBufferColorTransformZeroLayerAlpha
Bug: 157204341
Test: color inversion when switching pages in the Setting app
Test: RenderEngineTest
Change-Id: I206184aae84042290b00e411709e04e54579780a
diff --git a/libs/renderengine/gl/ProgramCache.cpp b/libs/renderengine/gl/ProgramCache.cpp
index 7fc0499..5ff9240 100644
--- a/libs/renderengine/gl/ProgramCache.cpp
+++ b/libs/renderengine/gl/ProgramCache.cpp
@@ -740,15 +740,6 @@
if (needs.isOpaque()) {
fs << "gl_FragColor.a = 1.0;";
}
- if (needs.hasAlpha()) {
- // modulate the current alpha value with alpha set
- if (needs.isPremultiplied()) {
- // ... and the color too if we're premultiplied
- fs << "gl_FragColor *= color.a;";
- } else {
- fs << "gl_FragColor.a *= color.a;";
- }
- }
}
if (needs.hasTransformMatrix() || (needs.getInputTF() != needs.getOutputTF()) ||
@@ -768,6 +759,23 @@
}
}
+ /*
+ * Whether applying layer alpha before or after color transform doesn't matter,
+ * as long as we can undo premultiplication. But we cannot un-premultiply
+ * for color transform if the layer alpha = 0, e.g. 0 / (0 + 0.0019) = 0.
+ */
+ if (!needs.drawShadows()) {
+ if (needs.hasAlpha()) {
+ // modulate the current alpha value with alpha set
+ if (needs.isPremultiplied()) {
+ // ... and the color too if we're premultiplied
+ fs << "gl_FragColor *= color.a;";
+ } else {
+ fs << "gl_FragColor.a *= color.a;";
+ }
+ }
+ }
+
if (needs.hasRoundedCorners()) {
if (needs.isPremultiplied()) {
fs << "gl_FragColor *= vec4(applyCornerRadius(outCropCoords));";
diff --git a/libs/renderengine/tests/RenderEngineTest.cpp b/libs/renderengine/tests/RenderEngineTest.cpp
index 712e5e2..d9dfd8c 100644
--- a/libs/renderengine/tests/RenderEngineTest.cpp
+++ b/libs/renderengine/tests/RenderEngineTest.cpp
@@ -406,6 +406,12 @@
void fillBufferColorTransform();
template <typename SourceVariant>
+ void fillBufferWithColorTransformZeroLayerAlpha();
+
+ template <typename SourceVariant>
+ void fillBufferColorTransformZeroLayerAlpha();
+
+ template <typename SourceVariant>
void fillRedBufferWithRoundedCorners();
template <typename SourceVariant>
@@ -765,6 +771,36 @@
}
template <typename SourceVariant>
+void RenderEngineTest::fillBufferWithColorTransformZeroLayerAlpha() {
+ renderengine::DisplaySettings settings;
+ settings.physicalDisplay = fullscreenRect();
+ settings.clip = Rect(1, 1);
+
+ std::vector<const renderengine::LayerSettings*> layers;
+
+ renderengine::LayerSettings layer;
+ layer.geometry.boundaries = Rect(1, 1).toFloatRect();
+ SourceVariant::fillColor(layer, 0.5f, 0.25f, 0.125f, this);
+ layer.alpha = 0;
+
+ // construct a fake color matrix
+ // simple inverse color
+ settings.colorTransform = mat4(-1, 0, 0, 0, 0, -1, 0, 0, 0, 0, -1, 0, 1, 1, 1, 1);
+
+ layer.geometry.boundaries = Rect(1, 1).toFloatRect();
+
+ layers.push_back(&layer);
+
+ invokeDraw(settings, layers, mBuffer);
+}
+
+template <typename SourceVariant>
+void RenderEngineTest::fillBufferColorTransformZeroLayerAlpha() {
+ fillBufferWithColorTransformZeroLayerAlpha<SourceVariant>();
+ expectBufferColor(fullscreenRect(), 0, 0, 0, 0);
+}
+
+template <typename SourceVariant>
void RenderEngineTest::fillRedBufferWithRoundedCorners() {
renderengine::DisplaySettings settings;
settings.physicalDisplay = fullscreenRect();
@@ -1240,6 +1276,13 @@
fillBufferWithRoundedCorners<ColorSourceVariant>();
}
+TEST_P(RenderEngineTest, drawLayers_fillBufferColorTransformZeroLayerAlpha_colorSource) {
+ const auto& renderEngineFactory = GetParam();
+ mRE = renderEngineFactory->createRenderEngine();
+
+ fillBufferColorTransformZeroLayerAlpha<ColorSourceVariant>();
+}
+
TEST_P(RenderEngineTest, drawLayers_fillBufferAndBlurBackground_colorSource) {
const auto& renderEngineFactory = GetParam();
mRE = renderEngineFactory->createRenderEngine();
@@ -1337,6 +1380,12 @@
fillBufferWithRoundedCorners<BufferSourceVariant<ForceOpaqueBufferVariant>>();
}
+TEST_P(RenderEngineTest, drawLayers_fillBufferColorTransformZeroLayerAlpha_opaqueBufferSource) {
+ const auto& renderEngineFactory = GetParam();
+ mRE = renderEngineFactory->createRenderEngine();
+
+ fillBufferColorTransformZeroLayerAlpha<BufferSourceVariant<ForceOpaqueBufferVariant>>();
+}
TEST_P(RenderEngineTest, drawLayers_fillBufferAndBlurBackground_opaqueBufferSource) {
const auto& renderEngineFactory = GetParam();
@@ -1436,6 +1485,13 @@
fillBufferWithRoundedCorners<BufferSourceVariant<RelaxOpaqueBufferVariant>>();
}
+TEST_P(RenderEngineTest, drawLayers_fillBufferColorTransformZeroLayerAlpha_bufferSource) {
+ const auto& renderEngineFactory = GetParam();
+ mRE = renderEngineFactory->createRenderEngine();
+
+ fillBufferColorTransformZeroLayerAlpha<BufferSourceVariant<RelaxOpaqueBufferVariant>>();
+}
+
TEST_P(RenderEngineTest, drawLayers_fillBufferAndBlurBackground_bufferSource) {
const auto& renderEngineFactory = GetParam();
mRE = renderEngineFactory->createRenderEngine();
