SF: fix off-by one in luma mean calculation
There was an off by one error in luma mean calculation that could
lead to segfault. Flaw was figured out in writing the 5 attached
unit tests for the function. Condition would be obscure in the wild,
but an exactly half-white, half-another-color in the sampled region
could present condition.
Fixes: 129858549
Test: libsurfaceflinger_unittest (5 new tests)
Change-Id: I920cd9cac15122178ec9258e33c9bc35b1bb9357
diff --git a/services/surfaceflinger/RegionSamplingThread.cpp b/services/surfaceflinger/RegionSamplingThread.cpp
index 718e996..35f11fc 100644
--- a/services/surfaceflinger/RegionSamplingThread.cpp
+++ b/services/surfaceflinger/RegionSamplingThread.cpp
@@ -266,6 +266,7 @@
constexpr auto rec709_blue_primary = 0.0722f;
return rec709_red_primary * r + rec709_green_primary * g + rec709_blue_primary * b;
}
+} // anonymous namespace
float sampleArea(const uint32_t* data, int32_t stride, const Rect& area) {
std::array<int32_t, 256> brightnessBuckets = {};
@@ -286,14 +287,13 @@
int32_t accumulated = 0;
size_t bucket = 0;
- while (bucket++ < brightnessBuckets.size()) {
+ for (; bucket < brightnessBuckets.size(); bucket++) {
accumulated += brightnessBuckets[bucket];
if (accumulated > majoritySampleNum) break;
}
return bucket / 255.0f;
}
-} // anonymous namespace
std::vector<float> RegionSamplingThread::sampleBuffer(
const sp<GraphicBuffer>& buffer, const Point& leftTop,