Split blur into low sample and high sample shaders.

Bug: 353826438
Test: atest BlurTests
Flag: com.android.graphics.surfaceflinger.flags.window_blur_kawase2

Change-Id: I5d1a4b34dc6419bd355251153042c0e8d76f8bde

Author: Shan Huang

libs/renderengine/skia/filters/KawaseBlurDualFilter.cpp

@@ -39,12 +39,36 @@ namespace renderengine {
 namespace skia {
 
 KawaseBlurDualFilter::KawaseBlurDualFilter() : BlurFilter() {
-    // A shader to sample each vertex of a unit regular heptagon
-    // plus the original fragment coordinate.
-    SkString blurString(R"(
+    // A shader to sample each vertex of a square, plus the original fragment coordinate,
+    // using a total of 5 samples.
+    SkString lowSampleBlurString(R"(
         uniform shader child;
         uniform float in_blurOffset;
         uniform float in_crossFade;
+        uniform float in_weightedCrossFade;
+
+        const float2 STEP_0 = float2( 0.707106781, 0.707106781);
+        const float2 STEP_1 = float2( 0.707106781, -0.707106781);
+        const float2 STEP_2 = float2(-0.707106781, -0.707106781);
+        const float2 STEP_3 = float2(-0.707106781, 0.707106781);
+
+        half4 main(float2 xy) {
+            half3 c = child.eval(xy).rgb;
+
+            c += child.eval(xy + STEP_0 * in_blurOffset).rgb;
+            c += child.eval(xy + STEP_1 * in_blurOffset).rgb;
+            c += child.eval(xy + STEP_2 * in_blurOffset).rgb;
+            c += child.eval(xy + STEP_3 * in_blurOffset).rgb;
+
+            return half4(c * in_weightedCrossFade, in_crossFade);
+        }
+    )");
+
+    // A shader to sample each vertex of a unit regular heptagon, plus the original fragment
+    // coordinate, using a total of 8 samples.
+    SkString highSampleBlurString(R"(
+        uniform shader child;
+        uniform float in_blurOffset;
 
         const float2 STEP_0 = float2( 1.0, 0.0);
         const float2 STEP_1 = float2( 0.623489802,  0.781831482);
@@ -65,39 +89,46 @@ KawaseBlurDualFilter::KawaseBlurDualFilter() : BlurFilter() {
             c += child.eval(xy + STEP_5 * in_blurOffset).rgb;
             c += child.eval(xy + STEP_6 * in_blurOffset).rgb;
 
-            return half4(c * 0.125 * in_crossFade, in_crossFade);
+            return half4(c * 0.125, 1.0);
         }
     )");
 
-    auto [blurEffect, error] = SkRuntimeEffect::MakeForShader(blurString);
-    LOG_ALWAYS_FATAL_IF(!blurEffect, "RuntimeShader error: %s", error.c_str());
-    mBlurEffect = std::move(blurEffect);
+    auto [lowSampleBlurEffect, error] = SkRuntimeEffect::MakeForShader(lowSampleBlurString);
+    auto [highSampleBlurEffect, error2] = SkRuntimeEffect::MakeForShader(highSampleBlurString);
+    LOG_ALWAYS_FATAL_IF(!lowSampleBlurEffect, "RuntimeShader error: %s", error.c_str());
+    LOG_ALWAYS_FATAL_IF(!highSampleBlurEffect, "RuntimeShader error: %s", error2.c_str());
+    mLowSampleBlurEffect = std::move(lowSampleBlurEffect);
+    mHighSampleBlurEffect = std::move(highSampleBlurEffect);
 }
 
 void KawaseBlurDualFilter::blurInto(const sk_sp<SkSurface>& drawSurface,
                                     const sk_sp<SkImage>& readImage, const float radius,
-                                    const float alpha) const {
+                                    const float alpha,
+                                    const sk_sp<SkRuntimeEffect>& blurEffect) const {
     const float scale = static_cast<float>(drawSurface->width()) / readImage->width();
     SkMatrix blurMatrix = SkMatrix::Scale(scale, scale);
     blurInto(drawSurface,
              readImage->makeShader(SkTileMode::kClamp, SkTileMode::kClamp,
                                    SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kNone),
                                    blurMatrix),
-             readImage->width() / static_cast<float>(drawSurface->width()), radius, alpha);
+             radius, alpha, blurEffect);
 }
 
 void KawaseBlurDualFilter::blurInto(const sk_sp<SkSurface>& drawSurface, sk_sp<SkShader> input,
-                                    const float inverseScale, const float radius,
-                                    const float alpha) const {
+                                    const float radius, const float alpha,
+                                    const sk_sp<SkRuntimeEffect>& blurEffect) const {
     SkPaint paint;
     if (radius == 0) {
         paint.setShader(std::move(input));
         paint.setAlphaf(alpha);
     } else {
-        SkRuntimeShaderBuilder blurBuilder(mBlurEffect);
+        SkRuntimeShaderBuilder blurBuilder(blurEffect);
         blurBuilder.child("child") = std::move(input);
+        if (blurEffect == mLowSampleBlurEffect) {
+            blurBuilder.uniform("in_crossFade") = alpha;
+            blurBuilder.uniform("in_weightedCrossFade") = alpha * 0.2f;
+        }
         blurBuilder.uniform("in_blurOffset") = radius;
-        blurBuilder.uniform("in_crossFade") = alpha;
         paint.setShader(blurBuilder.makeShader(nullptr));
     }
     paint.setBlendMode(alpha == 1.0f ? SkBlendMode::kSrc : SkBlendMode::kSrcOver);
@@ -163,16 +194,19 @@ sk_sp<SkImage> KawaseBlurDualFilter::generate(SkiaGpuContext* context, const uin
                 input->makeShader(SkTileMode::kClamp, SkTileMode::kClamp,
                                   SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kNone),
                                   blurMatrix);
-        blurInto(surfaces[0], std::move(sourceShader), kInputScale, kWeights[0] * step, 1.0f);
+        blurInto(surfaces[0], std::move(sourceShader), kWeights[0] * step, 1.0f,
+                 mLowSampleBlurEffect);
     }
     // Next the remaining downscale blur passes.
     for (int i = 0; i < filterPasses; i++) {
-        blurInto(surfaces[i + 1], surfaces[i]->makeTemporaryImage(), kWeights[1 + i] * step, 1.0f);
+        // Blur with the higher sample effect into the smaller buffers, for better visual quality.
+        blurInto(surfaces[i + 1], surfaces[i]->makeTemporaryImage(), kWeights[1 + i] * step, 1.0f,
+                 i == 0 ? mLowSampleBlurEffect : mHighSampleBlurEffect);
     }
     // Finally blur+upscale back to our original size.
     for (int i = filterPasses - 1; i >= 0; i--) {
         blurInto(surfaces[i], surfaces[i + 1]->makeTemporaryImage(), kWeights[4 - i] * step,
-                 std::min(1.0f, filterDepth - i));
+                 std::min(1.0f, filterDepth - i), mLowSampleBlurEffect);
     }
     return surfaces[0]->makeTemporaryImage();
 }

libs/renderengine/skia/filters/KawaseBlurDualFilter.h

@@ -41,13 +41,14 @@ class KawaseBlurDualFilter : public BlurFilter {
                             const sk_sp<SkImage> blurInput, const SkRect& blurRect) const override;
 
 private:
-    sk_sp<SkRuntimeEffect> mBlurEffect;
+    sk_sp<SkRuntimeEffect> mLowSampleBlurEffect;
+    sk_sp<SkRuntimeEffect> mHighSampleBlurEffect;
 
     void blurInto(const sk_sp<SkSurface>& drawSurface, const sk_sp<SkImage>& readImage,
-                  const float radius, const float alpha) const;
+                  const float radius, const float alpha, const sk_sp<SkRuntimeEffect>&) const;
 
     void blurInto(const sk_sp<SkSurface>& drawSurface, const sk_sp<SkShader> input,
-                  const float inverseScale, const float radius, const float alpha) const;
+                  const float radius, const float alpha, const sk_sp<SkRuntimeEffect>&) const;
 };
 
 } // namespace skia