Pass the radius as a float deeper into HWUI allowing RS to generate more accurate blurs.

Also, when converting radius to an integer value snap to the appropriate integer boundaries.

bug: 10650594
Change-Id: Icca4bc17d88162bbcbc6035d4f81bd1d98a4de2d

2 files changed, 17 insertions, 1 deletions

diff --git a/libs/hwui/utils/Blur.cpp b/libs/hwui/utils/Blur.cpp
index c020b40..877a422 100644
--- a/libs/hwui/utils/Blur.cpp
+++ b/libs/hwui/utils/Blur.cpp
@@ -19,6 +19,7 @@
 #include <math.h>
 
 #include "Blur.h"
+#include "MathUtils.h"
 
 namespace android {
 namespace uirenderer {
@@ -35,6 +36,17 @@ float Blur::convertSigmaToRadius(float sigma) {
     return sigma > 0.5f ? (sigma - 0.5f) / BLUR_SIGMA_SCALE : 0.0f;
 }
 
+// if the original radius was on an integer boundary and the resulting radius
+// is within the conversion error tolerance then we attempt to snap to the
+// original integer boundary.
+uint32_t Blur::convertRadiusToInt(float radius) {
+    const float radiusCeil  = ceilf(radius);
+    if (MathUtils::areEqual(radiusCeil, radius)) {
+        return radiusCeil;
+    }
+    return radius;
+}
+
 /**
  * HWUI has used a slightly different equation than Skia to generate the value
  * for sigma and to preserve compatibility we have kept that logic.
diff --git a/libs/hwui/utils/Blur.h b/libs/hwui/utils/Blur.h
index 79aff65..b145333 100644
--- a/libs/hwui/utils/Blur.h
+++ b/libs/hwui/utils/Blur.h
@@ -27,8 +27,12 @@ class Blur {
 public:
     // If radius > 0, return the corresponding sigma, else return 0
     ANDROID_API static float convertRadiusToSigma(float radius);
-    // If sigma > 0.6, return the corresponding radius, else return 0
+    // If sigma > 0.5, return the corresponding radius, else return 0
     ANDROID_API static float convertSigmaToRadius(float sigma);
+    // If the original radius was on an integer boundary then after the sigma to
+    // radius conversion a small rounding error may be introduced. This function
+    // accounts for that error and snaps to the appropriate integer boundary.
+    static uint32_t convertRadiusToInt(float radius);
 
     static void generateGaussianWeights(float* weights, int32_t radius);
     static void horizontal(float* weights, int32_t radius, const uint8_t* source,