Made shadows blurry (thru implementing variance mapping)

src/utils/SkShadowPaintFilterCanvas.cpp

Index: src/utils/SkShadowPaintFilterCanvas.cpp
diff --git a/src/utils/SkShadowPaintFilterCanvas.cpp b/src/utils/SkShadowPaintFilterCanvas.cpp
index 31b7661296151023a8266cf67d5d74468b181dc5..3c1f712a848e3f556a283b91cb4ed8b83b8353dc 100644
--- a/src/utils/SkShadowPaintFilterCanvas.cpp
+++ b/src/utils/SkShadowPaintFilterCanvas.cpp
@@ -11,7 +11,12 @@
 #ifdef SK_EXPERIMENTAL_SHADOWING
 
 SkShadowPaintFilterCanvas::SkShadowPaintFilterCanvas(SkCanvas *canvas)
-        : SkPaintFilterCanvas(canvas) { }
+        : SkPaintFilterCanvas(canvas) {
+    fShType.fShadowRadius = 0.0f;
+    fShType.fBlurAlgorithm = SkShadowType::kNoBlur_BlurAlgorithm;
+    fShType.fBiasingConstant = 0.0f;
+    fShType.fMinVariance = 0.0f;
+}
 
 // TODO use a shader instead
 bool SkShadowPaintFilterCanvas::onFilter(SkTCopyOnFirstWrite<SkPaint>* paint, Type type) const {
@@ -24,6 +29,15 @@ bool SkShadowPaintFilterCanvas::onFilter(SkTCopyOnFirstWrite<SkPaint>* paint, Ty
 
         SkColor color = 0xFF000000; // init color to opaque black
         color |= z; // Put the index into the blue component
+
+        if (fShType.fBlurAlgorithm == SkShadowType::kVariance_BlurAlgorithm) {
+            int z2 = z * z;
+            if (z2 > 255 * 256) {
+                color |= (255) << 8;
+            } else {
+                color |= (z2 / 256) << 8;

[jvanverth1, 2016/08/12 17:39:09]

I think (z2/256) << 8 is the same as (z2 & ~0xff). But if you use that, add a
comment to explain what's going on.

[vjiaoblack, 2016/08/12 19:07:42]

Done.

+            }
+        }
         newPaint.setColor(color);
 
         *paint->writable() = newPaint;
@@ -42,6 +56,9 @@ SkISize SkShadowPaintFilterCanvas::ComputeDepthMapSize(const SkLights::Light& li
     return SkISize::Make(dMapWidth, dMapHeight);
 }
 
+void SkShadowPaintFilterCanvas::setShadowType(SkShadowType sType) {
+    fShType = sType;
+}
 
 void SkShadowPaintFilterCanvas::onDrawPicture(const SkPicture *picture, const SkMatrix *matrix,
                                               const SkPaint *paint) {