[Impeller] Implement invert colors flag. (#39729)

* [Impeller] implement invert colors flag

* [Impeller] add invert colors support

Author: Jonah Williams

impeller/aiks/aiks_unittests.cc

@@ -82,6 +82,16 @@ TEST_P(AiksTest, CanRenderImage) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_P(AiksTest, CanRenderInvertedImage) {
+  Canvas canvas;
+  Paint paint;
+  auto image = std::make_shared<Image>(CreateTextureForFixture("kalimba.jpg"));
+  paint.color = Color::Red();
+  paint.invert_colors = true;
+  canvas.DrawImage(image, Point::MakeXY(100.0, 100.0), paint);
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 bool GenerateMipmap(const std::shared_ptr<Context>& context,
                     std::shared_ptr<Texture> texture,
                     std::string label) {

impeller/aiks/paint.cc

@@ -61,6 +61,7 @@ std::shared_ptr<Contents> Paint::WithFilters(
     const Matrix& effect_transform) const {
   bool is_solid_color_val = is_solid_color.value_or(!color_source);
   input = WithColorFilter(input);
+  input = WithInvertFilter(input);
   input = WithMaskBlur(input, is_solid_color_val, effect_transform);
   input = WithImageFilter(input, effect_transform);
   return input;
@@ -114,6 +115,28 @@ std::shared_ptr<Contents> Paint::WithColorFilter(
   return input;
 }
 
+/// A color matrix which inverts colors.
+// clang-format off
+constexpr ColorFilterContents::ColorMatrix kColorInversion = {
+  .array = {
+    -1.0,    0,    0, 1.0, 0, //
+       0, -1.0,    0, 1.0, 0, //
+       0,    0, -1.0, 1.0, 0, //
+     1.0,  1.0,  1.0, 1.0, 0  //
+  }
+};
+// clang-format on
+
+std::shared_ptr<Contents> Paint::WithInvertFilter(
+    std::shared_ptr<Contents> input) const {
+  if (!invert_colors) {
+    return input;
+  }
+
+  return ColorFilterContents::MakeColorMatrix(
+      {FilterInput::Make(std::move(input))}, kColorInversion);
+}
+
 std::shared_ptr<FilterContents> Paint::MaskBlurDescriptor::CreateMaskBlur(
     const FilterInput::Ref& input,
     bool is_solid_color,

impeller/aiks/paint.h

@@ -67,6 +67,7 @@ struct Paint {
   Scalar stroke_miter = 4.0;
   Style style = Style::kFill;
   BlendMode blend_mode = BlendMode::kSourceOver;
+  bool invert_colors = false;
 
   std::optional<ImageFilterProc> image_filter;
   std::optional<ColorFilterProc> color_filter;
@@ -123,6 +124,9 @@ struct Paint {
 
   std::shared_ptr<Contents> WithColorFilter(std::shared_ptr<Contents> input,
                                             bool absorb_opacity = false) const;
+
+  std::shared_ptr<Contents> WithInvertFilter(
+      std::shared_ptr<Contents> input) const;
 };
 
 }  // namespace impeller

impeller/display_list/display_list_dispatcher.cc

@@ -580,7 +580,7 @@ void DisplayListDispatcher::setColorFilter(
 
 // |flutter::Dispatcher|
 void DisplayListDispatcher::setInvertColors(bool invert) {
-  UNIMPLEMENTED;
+  paint_.invert_colors = invert;
 }
 
 // |flutter::Dispatcher|