Fixed ambient lighting calculations on SkLightingShader

src/core/SkLightingShader.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapProcShader.h"
 #include "SkBitmapProcState.h"
 #include "SkColor.h"
@@ skipping 162 matching lines @@
             this->emitChild(0, nullptr, &dstNormalName, args);
 
             fragBuilder->codeAppendf("vec3 normal = %s.xyz;", dstNormalName.c_str());
 
             // TODO: make this a loop and modulate the contribution from each light
             // based on the shadow map
             fragBuilder->codeAppendf("float NdotL = clamp(dot(normal, %s), 0.0, 1.0);",
                                      lightDirUniName);
             // diffuse light
             fragBuilder->codeAppendf("vec3 result = %s*diffuseColor.rgb*NdotL;", lightColorUniName);
-            // ambient light (multiplied by input color's alpha because we're working in premul'd
-            // space)
-            fragBuilder->codeAppendf("result += diffuseColor.a * %s;", ambientColorUniName);
+            // ambient light
+            fragBuilder->codeAppendf("result += %s * diffuseColor.rgb;", ambientColorUniName);
 
             // Clamping to alpha (equivalent to an unpremul'd clamp to 1.0)
             fragBuilder->codeAppendf("%s = vec4(clamp(result.rgb, 0.0, diffuseColor.a), "
                                                "diffuseColor.a);", args.fOutputColor);
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
                            GrProcessorKeyBuilder* b) {
 //            const LightingFP& lightingFP = proc.cast<LightingFP>();
             // only one shader generated currently
@@ skipping 176 matching lines @@
         for (int i = 0; i < n; ++i) {
             if (fDiffuseContext) {
                 diffColor = SkUnPreMultiply::PMColorToColor(diffuse[i]);
             }
 
             SkColor3f accum = SkColor3f::Make(0.0f, 0.0f, 0.0f);
             // This is all done in linear unpremul color space (each component 0..255.0f though)
             for (int l = 0; l < lightShader.fLights->numLights(); ++l) {
                 const SkLights::Light& light = lightShader.fLights->light(l);
 
-                if (SkLights::Light::kAmbient_LightType == light.type()) {
-                    accum += light.color().makeScale(255.0f);
-                } else {
-                    SkScalar NdotL = normals[i].dot(light.dir());
-                    if (NdotL < 0.0f) {
-                        NdotL = 0.0f;
+                SkScalar illuminanceScalingFactor = 1.0f;
+
+                if (SkLights::Light::kDirectional_LightType == light.type()) {
+                    illuminanceScalingFactor = normals[i].dot(light.dir());
+                    if (illuminanceScalingFactor < 0.0f) {
+                        illuminanceScalingFactor = 0.0f;
                     }
+                }
 
-                    accum.fX += light.color().fX * SkColorGetR(diffColor) * NdotL;
-                    accum.fY += light.color().fY * SkColorGetG(diffColor) * NdotL;
-                    accum.fZ += light.color().fZ * SkColorGetB(diffColor) * NdotL;
-                }
+                accum.fX += light.color().fX * SkColorGetR(diffColor) * illuminanceScalingFactor;
+                accum.fY += light.color().fY * SkColorGetG(diffColor) * illuminanceScalingFactor;
+                accum.fZ += light.color().fZ * SkColorGetB(diffColor) * illuminanceScalingFactor;
             }
 
             // convert() premultiplies the accumulate color with alpha
             result[i] = convert(accum, SkColorGetA(diffColor));
         }
 
         result += n;
         x += n;
         count -= n;
     } while (count > 0);
@@ skipping 121 matching lines @@
                                             std::move(lights));
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkLightingShader)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLightingShaderImpl)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ///////////////////////////////////////////////////////////////////////////////