[svg] Implement feGaussianBlur

This filter implementation should be complete, but note we are still
not quite passing the W3C filters-gauss-* tests because our filters
currently operate in sRGB and not linear RGB (which is quite noticable
in some of the blur tests).

Bug: skia:10841
Change-Id: I706cde879ef6eb47ce586279999536cf67237f13
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/352506
Commit-Queue: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

modules/svg/include/SkSVGFe.h

@@ -19,7 +19,8 @@ class SkSVGFe : public SkSVGHiddenContainer {
 public:
     static bool IsFilterEffect(const sk_sp<SkSVGNode>& node) {
         return node->tag() == SkSVGTag::kFeTurbulence || node->tag() == SkSVGTag::kFeColorMatrix ||
-               node->tag() == SkSVGTag::kFeComposite || node->tag() == SkSVGTag::kFeFlood;
+               node->tag() == SkSVGTag::kFeComposite || node->tag() == SkSVGTag::kFeFlood ||
+               node->tag() == SkSVGTag::kFeGaussianBlur;
     }
 
     sk_sp<SkImageFilter> makeImageFilter(const SkSVGRenderContext& ctx,

modules/svg/include/SkSVGFeGaussianBlur.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkSVGFeGaussianBlur_DEFINED
+#define SkSVGFeGaussianBlur_DEFINED
+
+#include "modules/svg/include/SkSVGFe.h"
+#include "modules/svg/include/SkSVGTypes.h"
+
+class SkSVGFeGaussianBlur : public SkSVGFe {
+public:
+    struct StdDeviation {
+        SkSVGNumberType fX;
+        SkSVGNumberType fY;
+    };
+
+    static sk_sp<SkSVGFeGaussianBlur> Make() {
+        return sk_sp<SkSVGFeGaussianBlur>(new SkSVGFeGaussianBlur());
+    }
+
+    SVG_ATTR(StdDeviation, StdDeviation, StdDeviation({0, 0}))
+
+protected:
+    sk_sp<SkImageFilter> onMakeImageFilter(const SkSVGRenderContext&,
+                                           const SkSVGFilterContext&) const override;
+
+    std::vector<SkSVGFeInputType> getInputs() const override { return {this->getIn()}; }
+
+    bool parseAndSetAttribute(const char*, const char*) override;
+
+private:
+    SkSVGFeGaussianBlur() : INHERITED(SkSVGTag::kFeGaussianBlur) {}
+
+    using INHERITED = SkSVGFe;
+};
+
+#endif  // SkSVGFeGaussianBlur_DEFINED

modules/svg/include/SkSVGNode.h

@@ -28,6 +28,7 @@ enum class SkSVGTag {
     kFeColorMatrix,
     kFeComposite,
     kFeFlood,
+    kFeGaussianBlur,
     kFeTurbulence,
     kFilter,
     kG,

modules/svg/src/SkSVGDOM.cpp

@@ -19,6 +19,7 @@
 #include "modules/svg/include/SkSVGFeColorMatrix.h"
 #include "modules/svg/include/SkSVGFeComposite.h"
 #include "modules/svg/include/SkSVGFeFlood.h"
+#include "modules/svg/include/SkSVGFeGaussianBlur.h"
 #include "modules/svg/include/SkSVGFeTurbulence.h"
 #include "modules/svg/include/SkSVGFilter.h"
 #include "modules/svg/include/SkSVGG.h"
@@ -260,6 +261,7 @@ SortedDictionaryEntry<sk_sp<SkSVGNode>(*)()> gTagFactories[] = {
     { "feColorMatrix" , []() -> sk_sp<SkSVGNode> { return SkSVGFeColorMatrix::Make();  }},
     { "feComposite"   , []() -> sk_sp<SkSVGNode> { return SkSVGFeComposite::Make();    }},
     { "feFlood"       , []() -> sk_sp<SkSVGNode> { return SkSVGFeFlood::Make();        }},
+    { "feGaussianBlur", []() -> sk_sp<SkSVGNode> { return SkSVGFeGaussianBlur::Make(); }},
     { "feTurbulence"  , []() -> sk_sp<SkSVGNode> { return SkSVGFeTurbulence::Make();   }},
     { "filter"        , []() -> sk_sp<SkSVGNode> { return SkSVGFilter::Make();         }},
     { "g"             , []() -> sk_sp<SkSVGNode> { return SkSVGG::Make();              }},

modules/svg/src/SkSVGFeGaussianBlur.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2020 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "include/effects/SkImageFilters.h"
+#include "modules/svg/include/SkSVGAttributeParser.h"
+#include "modules/svg/include/SkSVGFeGaussianBlur.h"
+#include "modules/svg/include/SkSVGFilterContext.h"
+#include "modules/svg/include/SkSVGRenderContext.h"
+#include "modules/svg/include/SkSVGValue.h"
+
+bool SkSVGFeGaussianBlur::parseAndSetAttribute(const char* name, const char* value) {
+    return INHERITED::parseAndSetAttribute(name, value) ||
+           this->setStdDeviation(SkSVGAttributeParser::parse<SkSVGFeGaussianBlur::StdDeviation>(
+                   "stdDeviation", name, value));
+}
+
+sk_sp<SkImageFilter> SkSVGFeGaussianBlur::onMakeImageFilter(const SkSVGRenderContext& ctx,
+                                                            const SkSVGFilterContext& fctx) const {
+    SkScalar sigmaX = fStdDeviation.fX;
+    SkScalar sigmaY = fStdDeviation.fY;
+    if (fctx.primitiveUnits().type() == SkSVGObjectBoundingBoxUnits::Type::kObjectBoundingBox) {
+        SkASSERT(ctx.node());
+        const SkRect objBounds = ctx.node()->objectBoundingBox(ctx);
+        sigmaX *= objBounds.width();
+        sigmaY *= objBounds.height();
+    }
+
+    return SkImageFilters::Blur(sigmaX, sigmaY,
+                                fctx.resolveInput(ctx, this->getIn()),
+                                this->resolveFilterSubregion(ctx, fctx));
+}
+
+template <>
+bool SkSVGAttributeParser::parse<SkSVGFeGaussianBlur::StdDeviation>(
+        SkSVGFeGaussianBlur::StdDeviation* stdDeviation) {
+    std::vector<SkSVGNumberType> values;
+    if (!this->parse(&values)) {
+        return false;
+    }
+
+    stdDeviation->fX = values[0];
+    stdDeviation->fY = values.size() > 1 ? values[1] : values[0];
+    return true;
+}

modules/svg/svg.gni

@@ -20,6 +20,7 @@ skia_svg_public = [
   "$_include/SkSVGFeColorMatrix.h",
   "$_include/SkSVGFeComposite.h",
   "$_include/SkSVGFeFlood.h",
+  "$_include/SkSVGFeGaussianBlur.h",
   "$_include/SkSVGFeTurbulence.h",
   "$_include/SkSVGFilter.h",
   "$_include/SkSVGFilterContext.h",
@@ -58,6 +59,7 @@ skia_svg_sources = [
   "$_src/SkSVGFeColorMatrix.cpp",
   "$_src/SkSVGFeComposite.cpp",
   "$_src/SkSVGFeFlood.cpp",
+  "$_src/SkSVGFeGaussianBlur.cpp",
   "$_src/SkSVGFeTurbulence.cpp",
   "$_src/SkSVGFilter.cpp",
   "$_src/SkSVGFilterContext.cpp",