Reland of Add fast normalize for SkLightingImageFilter.

src/effects/SkLightingImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLightingImageFilter.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 42 matching lines @@
 // Shift matrix components to the left, as we advance pixels to the right.
 inline void shiftMatrixLeft(int m[9]) {
     m[0] = m[1];
     m[3] = m[4];
     m[6] = m[7];
     m[1] = m[2];
     m[4] = m[5];
     m[7] = m[8];
 }
 
+static inline void fast_normalize(SkPoint3* vector) {
+    // add a tiny bit so we don't have to worry about divide-by-zero
+    SkScalar magSq = vector->dot(*vector) + SK_ScalarNearlyZero;
+    SkScalar scale = sk_float_rsqrt(magSq);
+    vector->fX *= scale;
+    vector->fY *= scale;
+    vector->fZ *= scale;
+}
+
 class DiffuseLightingType {
 public:
     DiffuseLightingType(SkScalar kd)
         : fKD(kd) {}
     SkPMColor light(const SkPoint3& normal, const SkPoint3& surfaceTolight,
                     const SkPoint3& lightColor) const {
         SkScalar colorScale = SkScalarMul(fKD, normal.dot(surfaceTolight));
         colorScale = SkScalarClampMax(colorScale, SK_Scalar1);
         SkPoint3 color = lightColor.makeScale(colorScale);
         return SkPackARGB32(255,
@@ skipping 10 matching lines @@
 }
 
 class SpecularLightingType {
 public:
     SpecularLightingType(SkScalar ks, SkScalar shininess)
         : fKS(ks), fShininess(shininess) {}
     SkPMColor light(const SkPoint3& normal, const SkPoint3& surfaceTolight,
                     const SkPoint3& lightColor) const {
         SkPoint3 halfDir(surfaceTolight);
         halfDir.fZ += SK_Scalar1;        // eye position is always (0, 0, 1)
-        halfDir.normalize();
+        fast_normalize(&halfDir);
         SkScalar colorScale = SkScalarMul(fKS,
             SkScalarPow(normal.dot(halfDir), fShininess));
         colorScale = SkScalarClampMax(colorScale, SK_Scalar1);
         SkPoint3 color = lightColor.makeScale(colorScale);
         return SkPackARGB32(SkClampMax(SkScalarRoundToInt(max_component(color)), 255),
                             SkClampMax(SkScalarRoundToInt(color.fX), 255),
                             SkClampMax(SkScalarRoundToInt(color.fY), 255),
                             SkClampMax(SkScalarRoundToInt(color.fZ), 255));
     }
 private:
     SkScalar fKS;
     SkScalar fShininess;
 };
 
 inline SkScalar sobel(int a, int b, int c, int d, int e, int f, SkScalar scale) {
     return SkScalarMul(SkIntToScalar(-a + b - 2 * c + 2 * d -e + f), scale);
 }
 
 inline SkPoint3 pointToNormal(SkScalar x, SkScalar y, SkScalar surfaceScale) {
     SkPoint3 vector = SkPoint3::Make(SkScalarMul(-x, surfaceScale),
                                      SkScalarMul(-y, surfaceScale),
                                      SK_Scalar1);
-    vector.normalize();
+    fast_normalize(&vector);
     return vector;
 }
 
 inline SkPoint3 topLeftNormal(int m[9], SkScalar surfaceScale) {
     return pointToNormal(sobel(0, 0, m[4], m[5], m[7], m[8], gTwoThirds),
                          sobel(0, 0, m[4], m[7], m[5], m[8], gTwoThirds),
                          surfaceScale);
 }
 
 inline SkPoint3 topNormal(int m[9], SkScalar surfaceScale) {
@@ skipping 666 matching lines @@
 class SkPointLight : public SkLight {
 public:
     SkPointLight(const SkPoint3& location, SkColor color)
      : INHERITED(color), fLocation(location) {}
 
     SkPoint3 surfaceToLight(int x, int y, int z, SkScalar surfaceScale) const {
         SkPoint3 direction = SkPoint3::Make(fLocation.fX - SkIntToScalar(x),
                                             fLocation.fY - SkIntToScalar(y),
                                             fLocation.fZ - SkScalarMul(SkIntToScalar(z),
                                                                        surfaceScale));
-        direction.normalize();
+        fast_normalize(&direction);
         return direction;
     };
     const SkPoint3& lightColor(const SkPoint3&) const { return this->color(); }
     LightType type() const override { return kPoint_LightType; }
     const SkPoint3& location() const { return fLocation; }
     GrGLLight* createGLLight() const override {
 #if SK_SUPPORT_GPU
         return SkNEW(GrGLPointLight);
 #else
         SkDEBUGFAIL("Should not call in GPU-less build");
@@ skipping 45 matching lines @@
                 const SkPoint3& target,
                 SkScalar specularExponent,
                 SkScalar cutoffAngle,
                 SkColor color)
      : INHERITED(color),
        fLocation(location),
        fTarget(target),
        fSpecularExponent(SkScalarPin(specularExponent, kSpecularExponentMin, kSpecularExponentMax))
     {
        fS = target - location;
-       fS.normalize();
+       fast_normalize(&fS);
        fCosOuterConeAngle = SkScalarCos(SkDegreesToRadians(cutoffAngle));
        const SkScalar antiAliasThreshold = 0.016f;
        fCosInnerConeAngle = fCosOuterConeAngle + antiAliasThreshold;
        fConeScale = SkScalarInvert(antiAliasThreshold);
     }
 
     SkLight* transform(const SkMatrix& matrix) const override {
         SkPoint location2 = SkPoint::Make(fLocation.fX, fLocation.fY);
         matrix.mapPoints(&location2, 1);
         // Use X scale and Y scale on Z and average the result
         SkPoint locationZ = SkPoint::Make(fLocation.fZ, fLocation.fZ);
         matrix.mapVectors(&locationZ, 1);
         SkPoint3 location = SkPoint3::Make(location2.fX, location2.fY,
                                            SkScalarAve(locationZ.fX, locationZ.fY));
         SkPoint target2 = SkPoint::Make(fTarget.fX, fTarget.fY);
         matrix.mapPoints(&target2, 1);
         SkPoint targetZ = SkPoint::Make(fTarget.fZ, fTarget.fZ);
         matrix.mapVectors(&targetZ, 1);
         SkPoint3 target = SkPoint3::Make(target2.fX, target2.fY,
                                          SkScalarAve(targetZ.fX, targetZ.fY));
         SkPoint3 s = target - location;
-        s.normalize();
+        fast_normalize(&s);
         return new SkSpotLight(location,
                                target,
                                fSpecularExponent,
                                fCosOuterConeAngle,
                                fCosInnerConeAngle,
                                fConeScale,
                                s,
                                color());
     }
 
     SkPoint3 surfaceToLight(int x, int y, int z, SkScalar surfaceScale) const {
         SkPoint3 direction = SkPoint3::Make(fLocation.fX - SkIntToScalar(x),
                                             fLocation.fY - SkIntToScalar(y),
                                             fLocation.fZ - SkScalarMul(SkIntToScalar(z),
                                                                        surfaceScale));
-        direction.normalize();
+        fast_normalize(&direction);
         return direction;
     };
     SkPoint3 lightColor(const SkPoint3& surfaceToLight) const {
         SkScalar cosAngle = -surfaceToLight.dot(fS);
         SkScalar scale = 0;
         if (cosAngle >= fCosOuterConeAngle) {
             scale = SkScalarPow(cosAngle, fSpecularExponent);
             if (cosAngle < fCosInnerConeAngle) {
                 scale = SkScalarMul(scale, cosAngle - fCosOuterConeAngle);
                 scale *= fConeScale;
@@ skipping 1097 matching lines @@
 
     fsBuilder->codeAppendf("%s(%s)", fLightColorFunc.c_str(), surfaceToLight);
 }
 
 #endif
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkLightingImageFilter)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkDiffuseLightingImageFilter)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkSpecularLightingImageFilter)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END