[skottie] Add tritone layer effect support

Generalize sksg::TintColorFilter into GradientColorfilter, to support
multiple color interpolation ranges.

Keep the two-color/single-matrix (tint) specialization, and use a table
color filter for the general case.

Change-Id: Idf42833462127c29fb69fe94337a1d1478b77dd9
Reviewed-on: https://skia-review.googlesource.com/c/194024
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>

modules/skottie/src/SkottieLayerEffect.cpp

@@ -45,7 +45,8 @@ sk_sp<sksg::RenderNode> AttachTintLayerEffect(const skjson::ArrayValue& jprops,
         return nullptr;
     }
 
-    auto tint_node = sksg::TintColorFilter::Make(std::move(layer),
+    auto tint_node =
+            sksg::GradientColorFilter::Make(std::move(layer),
                                             abuilder->attachColor(*color0_prop, ascope, "v"),
                                             abuilder->attachColor(*color1_prop, ascope, "v"));
     if (!tint_node) {
@@ -60,6 +61,49 @@ sk_sp<sksg::RenderNode> AttachTintLayerEffect(const skjson::ArrayValue& jprops,
     return std::move(tint_node);
 }
 
+sk_sp<sksg::RenderNode> AttachTritoneLayerEffect(const skjson::ArrayValue& jprops,
+                                                 const AnimationBuilder* abuilder,
+                                                 AnimatorScope* ascope,
+                                                 sk_sp<sksg::RenderNode> layer) {
+    enum : size_t {
+        kHiColor_Index     = 0,
+        kMiColor_Index     = 1,
+        kLoColor_Index     = 2,
+        kBlendAmount_Index = 3,
+
+        kMax_Index      = kBlendAmount_Index,
+    };
+
+    if (jprops.size() <= kMax_Index) {
+        return nullptr;
+    }
+
+    const skjson::ObjectValue* hicolor_prop = jprops[    kHiColor_Index];
+    const skjson::ObjectValue* micolor_prop = jprops[    kMiColor_Index];
+    const skjson::ObjectValue* locolor_prop = jprops[    kLoColor_Index];
+    const skjson::ObjectValue*   blend_prop = jprops[kBlendAmount_Index];
+
+    if (!hicolor_prop || !micolor_prop || !locolor_prop || !blend_prop) {
+        return nullptr;
+    }
+
+    auto tritone_node =
+            sksg::GradientColorFilter::Make(std::move(layer), {
+                                            abuilder->attachColor(*locolor_prop, ascope, "v"),
+                                            abuilder->attachColor(*micolor_prop, ascope, "v"),
+                                            abuilder->attachColor(*hicolor_prop, ascope, "v") });
+    if (!tritone_node) {
+        return nullptr;
+    }
+
+    abuilder->bindProperty<ScalarValue>((*blend_prop)["v"], ascope,
+        [tritone_node](const ScalarValue& w) {
+            tritone_node->setWeight((100 - w) / 100); // 100-based, inverted (!?).
+        });
+
+    return std::move(tritone_node);
+}
+
 sk_sp<sksg::RenderNode> AttachFillLayerEffect(const skjson::ArrayValue& jprops,
                                               const AnimationBuilder* abuilder,
                                               AnimatorScope* ascope,
@@ -181,6 +225,7 @@ sk_sp<sksg::RenderNode> AnimationBuilder::attachLayerEffects(const skjson::Array
     enum : int32_t {
         kTint_Effect       = 20,
         kFill_Effect       = 21,
+        kTritone_Effect    = 23,
         kDropShadow_Effect = 25,
     };
 
@@ -201,6 +246,9 @@ sk_sp<sksg::RenderNode> AnimationBuilder::attachLayerEffects(const skjson::Array
         case kFill_Effect:
             layer = AttachFillLayerEffect(*jprops, this, ascope, std::move(layer));
             break;
+        case kTritone_Effect:
+            layer = AttachTritoneLayerEffect(*jprops, this, ascope, std::move(layer));
+            break;
         case kDropShadow_Effect:
             layer = AttachDropShadowLayerEffect(*jprops, this, ascope, std::move(layer));
             break;

modules/sksg/include/SkSGColorFilter.h

@@ -12,6 +12,8 @@
 
 #include "SkBlendMode.h"
 
+#include <vector>
+
 class SkColorFilter;
 
 namespace sksg {
@@ -62,17 +64,18 @@ private:
 };
 
 /**
- * Tint color effect: maps RGB colors to the [c0,c1] gradient based on input luminance
+ * Tint/multi-tone color effect: maps RGB colors to the [C0,C1][C1,C2]..[Cn-1,Cn] gradient
- * (while leaving the alpha channel unchanged), then mixes with the input based on weight.
+ * based on input luminance (where the colors are evenly distributed across the luminance domain),
+ * then mixes with the input based on weight.  Leaves alpha unchanged.
  */
-
+class GradientColorFilter final : public ColorFilter {
-class TintColorFilter final : public ColorFilter {
 public:
-    ~TintColorFilter() override;
+    ~GradientColorFilter() override;
 
-    static sk_sp<TintColorFilter> Make(sk_sp<RenderNode> child,
+    static sk_sp<GradientColorFilter> Make(sk_sp<RenderNode> child,
-                                       sk_sp<Color> color0,
+                                           sk_sp<Color> c0, sk_sp<Color> c1);
-                                       sk_sp<Color> color1);
+    static sk_sp<GradientColorFilter> Make(sk_sp<RenderNode> child,
+                                           std::vector<sk_sp<Color>>);
 
     SG_ATTRIBUTE(Weight, float, fWeight)
 
@@ -80,14 +83,13 @@ protected:
     sk_sp<SkColorFilter> onRevalidateFilter() override;
 
 private:
-    TintColorFilter(sk_sp<RenderNode>, sk_sp<Color>, sk_sp<Color>);
+    GradientColorFilter(sk_sp<RenderNode>, std::vector<sk_sp<Color>>);
 
-    const sk_sp<Color> fColor0,
+    const std::vector<sk_sp<Color>> fColors;
-                       fColor1;
 
     float                           fWeight = 0;
 
-    typedef ColorFilter INHERITED;
+    using INHERITED = ColorFilter;
 };
 
 } // namespace sksg

modules/sksg/src/SkSGColorFilter.cpp

@@ -9,6 +9,9 @@
 
 #include "SkColorFilter.h"
 #include "SkSGColor.h"
+#include "SkTableColorFilter.h"
+
+#include <cmath>
 
 namespace sksg {
 
@@ -57,48 +60,49 @@ sk_sp<SkColorFilter> ModeColorFilter::onRevalidateFilter() {
     return SkColorFilter::MakeModeFilter(fColor->getColor(), fMode);
 }
 
-sk_sp<TintColorFilter> TintColorFilter::Make(sk_sp<RenderNode> child,
+sk_sp<GradientColorFilter> GradientColorFilter::Make(sk_sp<RenderNode> child,
                                                      sk_sp<Color> c0, sk_sp<Color> c1) {
-    return (child && c0 && c1) ? sk_sp<TintColorFilter>(new TintColorFilter(std::move(child),
+    return Make(std::move(child), { std::move(c0), std::move(c1) });
-                                                                            std::move(c0),
+}
-                                                                            std::move(c1)))
+
+sk_sp<GradientColorFilter> GradientColorFilter::Make(sk_sp<RenderNode> child,
+                                                     std::vector<sk_sp<Color>> colors) {
+    return (child && colors.size() > 1)
+        ? sk_sp<GradientColorFilter>(new GradientColorFilter(std::move(child), std::move(colors)))
         : nullptr;
 }
 
-TintColorFilter::TintColorFilter(sk_sp<RenderNode> child, sk_sp<Color> c0, sk_sp<Color> c1)
+GradientColorFilter::GradientColorFilter(sk_sp<RenderNode> child, std::vector<sk_sp<Color>> colors)
     : INHERITED(std::move(child))
-    , fColor0(std::move(c0))
+    , fColors(std::move(colors)) {
-    , fColor1(std::move(c1)) {
+    for (const auto& color : fColors) {
-    this->observeInval(fColor0);
+        this->observeInval(color);
-    this->observeInval(fColor1);
+    }
 }
 
-TintColorFilter::~TintColorFilter() {
+GradientColorFilter::~GradientColorFilter() {
-    this->unobserveInval(fColor0);
+    for (const auto& color : fColors) {
-    this->unobserveInval(fColor1);
+        this->unobserveInval(color);
+    }
 }
 
-sk_sp<SkColorFilter> TintColorFilter::onRevalidateFilter() {
+namespace  {
-    fColor0->revalidate(nullptr, SkMatrix::I());
-    fColor1->revalidate(nullptr, SkMatrix::I());
-
-    if (fWeight <= 0) {
-        return nullptr;
-    }
-
-    const auto c0 = SkColor4f::FromColor(fColor0->getColor()),
-               c1 = SkColor4f::FromColor(fColor1->getColor());
 
 // luminance coefficients
 static constexpr float kR = 0.2126f,
                        kG = 0.7152f,
                        kB = 0.0722f;
 
+sk_sp<SkColorFilter> Make2ColorGradient(const sk_sp<Color>& color0, const sk_sp<Color>& color1) {
+    const auto c0 = SkColor4f::FromColor(color0->getColor()),
+               c1 = SkColor4f::FromColor(color1->getColor());
+
     const auto dR = c1.fR - c0.fR,
                dG = c1.fG - c0.fG,
                dB = c1.fB - c0.fB;
 
-    // First, we need a luminance:
+    // A 2-color gradient can be expressed as a color matrix (and combined with the luminance
+    // calculation).  First, the luminance:
     //
     //   L = [r,g,b] . [kR,kG,kB]
     //
@@ -132,9 +136,77 @@ sk_sp<SkColorFilter> TintColorFilter::onRevalidateFilter() {
             0,     0,     0, 1,           0,
     };
 
-    return SkColorFilter::MakeMixer(nullptr,
+    return SkColorFilter::MakeMatrixFilterRowMajor255(tint_matrix);
-                                    SkColorFilter::MakeMatrixFilterRowMajor255(tint_matrix),
+}
-                                    fWeight);
+
+sk_sp<SkColorFilter> MakeNColorGradient(const std::vector<sk_sp<Color>>& colors) {
+    // For N colors, we build a gradient color table.
+    uint8_t rTable[256], gTable[256], bTable[256];
+
+    SkASSERT(colors.size() > 2);
+    const auto span_count = colors.size() - 1;
+
+    size_t span_start = 0;
+    for (size_t i = 0; i < span_count; ++i) {
+        const auto span_stop = static_cast<size_t>(std::round((i + 1) * 255.0f / span_count)),
+                   span_size = span_stop - span_start;
+        if (span_start > span_stop) {
+            // Degenerate case.
+            continue;
+        }
+        SkASSERT(span_stop <= 255);
+
+        // Fill the gradient in [span_start,span_stop] -> [c0,c1]
+        const SkColor c0 = colors[i    ]->getColor(),
+                      c1 = colors[i + 1]->getColor();
+        float r = SkColorGetR(c0),
+              g = SkColorGetG(c0),
+              b = SkColorGetB(c0);
+        const float dR = (SkColorGetR(c1) - r) / span_size,
+                    dG = (SkColorGetG(c1) - g) / span_size,
+                    dB = (SkColorGetB(c1) - b) / span_size;
+
+        for (size_t j = span_start; j <= span_stop; ++j) {
+            rTable[j] = static_cast<uint8_t>(std::round(r));
+            gTable[j] = static_cast<uint8_t>(std::round(g));
+            bTable[j] = static_cast<uint8_t>(std::round(b));
+            r += dR;
+            g += dG;
+            b += dB;
+        }
+
+        // Ensure we always advance.
+        span_start = span_stop + 1;
+    }
+    SkASSERT(span_start == 256);
+
+    const SkScalar luminance_matrix[] = {
+        kR, kG, kB,  0,  0,  // r' = L
+        kR, kG, kB,  0,  0,  // g' = L
+        kR, kG, kB,  0,  0,  // b' = L
+         0,  0,  0,  1,  0,  // a' = a
+    };
+
+    return SkTableColorFilter::MakeARGB(nullptr, rTable, gTable, bTable)
+            ->makeComposed(SkColorFilter::MakeMatrixFilterRowMajor255(luminance_matrix));
+}
+
+} // namespace
+
+sk_sp<SkColorFilter> GradientColorFilter::onRevalidateFilter() {
+    for (const auto& color : fColors) {
+        color->revalidate(nullptr, SkMatrix::I());
+    }
+
+    if (fWeight <= 0) {
+        return nullptr;
+    }
+
+    SkASSERT(fColors.size() > 1);
+    auto gradientCF = (fColors.size() > 2) ? MakeNColorGradient(fColors)
+                                           : Make2ColorGradient(fColors[0], fColors[1]);
+
+    return SkColorFilter::MakeMixer(nullptr, std::move(gradientCF), fWeight);
 }
 
 } // namespace sksg