Add tonal color support for shadows.

Bug: skia:
Change-Id: Ib9bd9083da1d8a9fa90ae7c710386e6903541fd5
Reviewed-on: https://skia-review.googlesource.com/18148
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

1 files changed, 26 insertions, 5 deletions

diff --git a/src/utils/SkShadowUtils.cpp b/src/utils/SkShadowUtils.cpp
index 4b5ed5f168..c5b04f311b 100644
--- a/src/utils/SkShadowUtils.cpp
+++ b/src/utils/SkShadowUtils.cpp
@@ -528,7 +528,24 @@ static SkPoint3 map(const SkMatrix& m, const SkPoint3& pt) {
     return result;
 }
 
-static SkColor compute_render_color(SkColor color, float alpha) {
+static SkColor compute_render_color(SkColor color, float alpha, bool useTonalColor) {
+    if (useTonalColor) {
+        SkScalar colorScale;
+        SkScalar tonalAlpha;
+        SkColor4f color4f = SkColor4f::FromColor(color);
+        SkShadowUtils::ComputeTonalColorParams(color4f.fR,
+                                               color4f.fG,
+                                               color4f.fB,
+                                               alpha,
+                                               &colorScale, &tonalAlpha);
+        // After pre-multiplying, we want the alpha to be scaled by tonalAlpha, and
+        // the color scaled by colorScale. This scale factor gives that.
+        SkScalar unPremulScale = colorScale / tonalAlpha;
+
+        return SkColorSetARGB(tonalAlpha*255.999f, unPremulScale*SkColorGetR(color),
+                              unPremulScale*SkColorGetG(color), unPremulScale*SkColorGetB(color));
+    }
+
     return SkColorSetARGB(alpha*SkColorGetA(color), SkColorGetR(color),
                           SkColorGetG(color), SkColorGetB(color));
 }
@@ -572,6 +589,7 @@ void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
     bool tiltZPlane = tilted(rec.fZPlaneParams);
     bool transparent = SkToBool(rec.fFlags & SkShadowFlags::kTransparentOccluder_ShadowFlag);
     bool uncached = tiltZPlane || path.isVolatile();
+    bool useTonalColor = SkToBool(rec.fFlags & kTonalColor_ShadowFlag);
 
     SkColor color = rec.fColor;
     SkPoint3 zPlaneParams = rec.fZPlaneParams;
@@ -581,11 +599,16 @@ void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
     float ambientAlpha = rec.fAmbientAlpha;
     if (ambientAlpha > 0) {
         ambientAlpha = SkTMin(ambientAlpha, 1.f);
+        SkColor renderColor;
+        if (useTonalColor) {
+            renderColor = compute_render_color(SK_ColorBLACK, ambientAlpha, false);
+        } else {
+            renderColor = compute_render_color(color, ambientAlpha, false);
+        }
         if (uncached) {
             sk_sp<SkVertices> vertices = SkShadowTessellator::MakeAmbient(path, viewMatrix,
                                                                           zPlaneParams,
                                                                           transparent);
-            SkColor renderColor = compute_render_color(color, ambientAlpha);
             SkPaint paint;
             // Run the vertex color through a GaussianColorFilter and then modulate the grayscale
             // result of that against our 'color' param.
@@ -604,7 +627,6 @@ void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
                 factory.fOffset.fY = viewMatrix.getTranslateY();
             }
 
-            SkColor renderColor = compute_render_color(color, ambientAlpha);
             draw_shadow(factory, drawVertsProc, shadowedPath, renderColor);
         }
     }
@@ -612,12 +634,12 @@ void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
     float spotAlpha = rec.fSpotAlpha;
     if (spotAlpha > 0) {
         spotAlpha = SkTMin(spotAlpha, 1.f);
+        SkColor renderColor = compute_render_color(color, spotAlpha, useTonalColor);
         if (uncached) {
             sk_sp<SkVertices> vertices = SkShadowTessellator::MakeSpot(path, viewMatrix,
                                                                        zPlaneParams,
                                                                        devLightPos, lightRadius,
                                                                        transparent);
-            SkColor renderColor = compute_render_color(color, spotAlpha);
             SkPaint paint;
             // Run the vertex color through a GaussianColorFilter and then modulate the grayscale
             // result of that against our 'color' param.
@@ -671,7 +693,6 @@ void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
                     break;
             }
 #endif
-            SkColor renderColor = compute_render_color(color, spotAlpha);
             draw_shadow(factory, drawVertsProc, shadowedPath, renderColor);
         }
     }