Add blur styles to gaussian blur (flutter#107)

Author: bdero

impeller/entity/contents/filters/filter_contents.cc

@@ -61,20 +61,26 @@ std::shared_ptr<FilterContents> FilterContents::MakeBlend(
 
 std::shared_ptr<FilterContents> FilterContents::MakeDirectionalGaussianBlur(
     FilterInput::Ref input,
-    Vector2 blur_vector) {
+    Vector2 blur_vector,
+    BlurStyle blur_style,
+    FilterInput::Ref source_override) {
   auto blur = std::make_shared<DirectionalGaussianBlurFilterContents>();
   blur->SetInputs({input});
   blur->SetBlurVector(blur_vector);
+  blur->SetBlurStyle(blur_style);
+  blur->SetSourceOverride(source_override);
   return blur;
 }
 
 std::shared_ptr<FilterContents> FilterContents::MakeGaussianBlur(
     FilterInput::Ref input,
     Scalar sigma_x,
-    Scalar sigma_y) {
-  auto x_blur = MakeDirectionalGaussianBlur(input, Point(sigma_x, 0));
-  auto y_blur =
-      MakeDirectionalGaussianBlur(FilterInput::Make(x_blur), Point(0, sigma_y));
+    Scalar sigma_y,
+    BlurStyle blur_style) {
+  auto x_blur =
+      MakeDirectionalGaussianBlur(input, Point(sigma_x, 0), BlurStyle::kNormal);
+  auto y_blur = MakeDirectionalGaussianBlur(
+      FilterInput::Make(x_blur), Point(0, sigma_y), blur_style, input);
   return y_blur;
 }
 

impeller/entity/contents/filters/filter_contents.h

@@ -18,15 +18,31 @@ class Pipeline;
 
 class FilterContents : public Contents {
  public:
+  enum class BlurStyle {
+    /// Blurred inside and outside.
+    kNormal,
+    /// Solid inside, blurred outside.
+    kSolid,
+    /// Nothing inside, blurred outside.
+    kOuter,
+    /// Blurred inside, nothing outside.
+    kInner,
+  };
+
   static std::shared_ptr<FilterContents> MakeBlend(Entity::BlendMode blend_mode,
                                                    FilterInput::Vector inputs);
 
   static std::shared_ptr<FilterContents> MakeDirectionalGaussianBlur(
       FilterInput::Ref input,
-      Vector2 blur_vector);
+      Vector2 blur_vector,
+      BlurStyle blur_style = BlurStyle::kNormal,
+      FilterInput::Ref alpha_mask = nullptr);
 
-  static std::shared_ptr<FilterContents>
-  MakeGaussianBlur(FilterInput::Ref input, Scalar sigma_x, Scalar sigma_y);
+  static std::shared_ptr<FilterContents> MakeGaussianBlur(
+      FilterInput::Ref input,
+      Scalar sigma_x,
+      Scalar sigma_y,
+      BlurStyle blur_style = BlurStyle::kNormal);
 
   FilterContents();
 

impeller/entity/contents/filters/gaussian_blur_filter_contents.cc

@@ -30,6 +30,38 @@ void DirectionalGaussianBlurFilterContents::SetBlurVector(Vector2 blur_vector) {
   blur_vector_ = blur_vector;
 }
 
+void DirectionalGaussianBlurFilterContents::SetBlurStyle(BlurStyle blur_style) {
+  blur_style_ = blur_style;
+
+  switch (blur_style) {
+    case FilterContents::BlurStyle::kNormal:
+      src_color_factor_ = false;
+      inner_blur_factor_ = true;
+      outer_blur_factor_ = true;
+      break;
+    case FilterContents::BlurStyle::kSolid:
+      src_color_factor_ = true;
+      inner_blur_factor_ = false;
+      outer_blur_factor_ = true;
+      break;
+    case FilterContents::BlurStyle::kOuter:
+      src_color_factor_ = false;
+      inner_blur_factor_ = false;
+      outer_blur_factor_ = true;
+      break;
+    case FilterContents::BlurStyle::kInner:
+      src_color_factor_ = false;
+      inner_blur_factor_ = true;
+      outer_blur_factor_ = false;
+      break;
+  }
+}
+
+void DirectionalGaussianBlurFilterContents::SetSourceOverride(
+    FilterInput::Ref alpha_mask) {
+  source_override_ = alpha_mask;
+}
+
 bool DirectionalGaussianBlurFilterContents::RenderFilter(
     const FilterInput::Vector& inputs,
     const ContentContext& renderer,
@@ -45,43 +77,59 @@ bool DirectionalGaussianBlurFilterContents::RenderFilter(
 
   auto& host_buffer = pass.GetTransientsBuffer();
 
-  // Because this filter is intended to be used with only one input parameter,
-  // and GetBounds just increases the input size by a factor of the direction,
-  // we we can just scale up the UVs by the same amount and don't need to worry
-  // about mapping the UVs to the destination rect (like we do in
-  // BlendFilterContents).
-
   auto input = inputs[0]->GetSnapshot(renderer, entity);
-  auto input_size = input->texture->GetSize();
+  auto input_bounds = inputs[0]->GetBounds(entity);
+  auto filter_bounds = GetBounds(entity);
 
   auto transformed_blur =
       entity.GetTransformation().TransformDirection(blur_vector_);
 
-  auto uv_offset = transformed_blur.Abs() / input_size;
   // LTRB
   Scalar uv[4] = {
-      -uv_offset.x,
-      -uv_offset.y,
-      1 + uv_offset.x,
-      1 + uv_offset.y,
+      (filter_bounds.GetLeft() - input_bounds.GetLeft()) /
+          input_bounds.size.width,
+      (filter_bounds.GetTop() - input_bounds.GetTop()) /
+          input_bounds.size.height,
+      1 + (filter_bounds.GetRight() - input_bounds.GetRight()) /
+              input_bounds.size.width,
+      1 + (filter_bounds.GetBottom() - input_bounds.GetBottom()) /
+              input_bounds.size.height,
+  };
+
+  auto source = source_override_ ? source_override_ : inputs[0];
+  auto source_texture = source->GetSnapshot(renderer, entity);
+  auto source_bounds = source->GetBounds(entity);
+
+  // LTRB
+  Scalar uv_src[4] = {
+      (filter_bounds.GetLeft() - source_bounds.GetLeft()) /
+          source_bounds.size.width,
+      (filter_bounds.GetTop() - source_bounds.GetTop()) /
+          source_bounds.size.height,
+      1 + (filter_bounds.GetRight() - source_bounds.GetRight()) /
+              source_bounds.size.width,
+      1 + (filter_bounds.GetBottom() - source_bounds.GetBottom()) /
+              source_bounds.size.height,
   };
 
   VertexBufferBuilder<VS::PerVertexData> vtx_builder;
-  auto size = pass.GetRenderTargetSize();
   vtx_builder.AddVertices({
-      {Point(0, 0), Point(uv[0], uv[1])},
-      {Point(size.width, 0), Point(uv[2], uv[1])},
-      {Point(size.width, size.height), Point(uv[2], uv[3])},
-      {Point(0, 0), Point(uv[0], uv[1])},
-      {Point(size.width, size.height), Point(uv[2], uv[3])},
-      {Point(0, size.height), Point(uv[0], uv[3])},
+      {Point(0, 0), Point(uv[0], uv[1]), Point(uv_src[0], uv_src[1])},
+      {Point(1, 0), Point(uv[2], uv[1]), Point(uv_src[2], uv_src[1])},
+      {Point(1, 1), Point(uv[2], uv[3]), Point(uv_src[2], uv_src[3])},
+      {Point(0, 0), Point(uv[0], uv[1]), Point(uv_src[0], uv_src[1])},
+      {Point(1, 1), Point(uv[2], uv[3]), Point(uv_src[2], uv_src[3])},
+      {Point(0, 1), Point(uv[0], uv[3]), Point(uv_src[0], uv_src[3])},
   });
   auto vtx_buffer = vtx_builder.CreateVertexBuffer(host_buffer);
 
   VS::FrameInfo frame_info;
-  frame_info.texture_size = Point(input_size);
+  frame_info.texture_size = Point(input_bounds.size);
   frame_info.blur_radius = transformed_blur.GetLength();
   frame_info.blur_direction = transformed_blur.Normalize();
+  frame_info.src_factor = src_color_factor_;
+  frame_info.inner_blur_factor = inner_blur_factor_;
+  frame_info.outer_blur_factor = outer_blur_factor_;
 
   auto sampler = renderer.GetContext()->GetSamplerLibrary()->GetSampler({});
 
@@ -93,8 +141,9 @@ bool DirectionalGaussianBlurFilterContents::RenderFilter(
   cmd.BindVertices(vtx_buffer);
 
   FS::BindTextureSampler(cmd, input->texture, sampler);
+  FS::BindAlphaMaskSampler(cmd, source_texture->texture, sampler);
 
-  frame_info.mvp = Matrix::MakeOrthographic(size);
+  frame_info.mvp = Matrix::MakeOrthographic(ISize(1, 1));
   auto uniform_view = host_buffer.EmplaceUniform(frame_info);
   VS::BindFrameInfo(cmd, uniform_view);
 

impeller/entity/contents/filters/gaussian_blur_filter_contents.h

@@ -4,6 +4,8 @@
 
 #pragma once
 
+#include <memory>
+#include <optional>
 #include "impeller/entity/contents/filters/filter_contents.h"
 #include "impeller/entity/contents/filters/filter_input.h"
 #include "impeller/geometry/matrix.h"
@@ -18,6 +20,10 @@ class DirectionalGaussianBlurFilterContents final : public FilterContents {
 
   void SetBlurVector(Vector2 blur_vector);
 
+  void SetBlurStyle(BlurStyle blur_style);
+
+  void SetSourceOverride(FilterInput::Ref alpha_mask);
+
   // |Contents|
   Rect GetBounds(const Entity& entity) const override;
 
@@ -30,6 +36,11 @@ class DirectionalGaussianBlurFilterContents final : public FilterContents {
                     const Rect& bounds) const override;
 
   Vector2 blur_vector_;
+  BlurStyle blur_style_ = BlurStyle::kNormal;
+  bool src_color_factor_ = false;
+  bool inner_blur_factor_ = true;
+  bool outer_blur_factor_ = true;
+  FilterInput::Ref source_override_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(DirectionalGaussianBlurFilterContents);
 };

impeller/entity/entity_unittests.cc

@@ -689,11 +689,18 @@ TEST_F(EntityTest, GaussianBlurFilter) {
   auto callback = [&](ContentContext& context, RenderPass& pass) -> bool {
     if (first_frame) {
       first_frame = false;
-      ImGui::SetNextWindowSize({500, 190});
+      ImGui::SetNextWindowSize({500, 220});
       ImGui::SetNextWindowPos({300, 550});
     }
 
+    const char* blur_style_names[] = {"Normal", "Solid", "Outer", "Inner"};
+    const FilterContents::BlurStyle blur_styles[] = {
+        FilterContents::BlurStyle::kNormal, FilterContents::BlurStyle::kSolid,
+        FilterContents::BlurStyle::kOuter, FilterContents::BlurStyle::kInner};
+
+    // UI state.
     static float blur_amount[2] = {20, 20};
+    static int selected_blur_style = 0;
     static Color cover_color(1, 0, 0, 0.2);
     static Color bounds_color(0, 1, 0, 0.1);
     static float offset[2] = {500, 400};
@@ -702,21 +709,27 @@ TEST_F(EntityTest, GaussianBlurFilter) {
     static float skew[2] = {0, 0};
 
     ImGui::Begin("Controls");
-    ImGui::SliderFloat2("Blur", &blur_amount[0], 0, 200);
-    ImGui::ColorEdit4("Cover color", reinterpret_cast<float*>(&cover_color));
-    ImGui::ColorEdit4("Bounds color", reinterpret_cast<float*>(&bounds_color));
-    ImGui::SliderFloat2("Translation", &offset[0], 0,
-                        pass.GetRenderTargetSize().width);
-    ImGui::SliderFloat("Rotation", &rotation, 0, kPi * 2);
-    ImGui::SliderFloat2("Scale", &scale[0], 0, 3);
-    ImGui::SliderFloat2("Skew", &skew[0], -3, 3);
+    {
+      ImGui::SliderFloat2("Blur", &blur_amount[0], 0, 200);
+      ImGui::Combo("Blur style", &selected_blur_style, blur_style_names,
+                   sizeof(blur_style_names) / sizeof(char*));
+      ImGui::ColorEdit4("Cover color", reinterpret_cast<float*>(&cover_color));
+      ImGui::ColorEdit4("Bounds color",
+                        reinterpret_cast<float*>(&bounds_color));
+      ImGui::SliderFloat2("Translation", &offset[0], 0,
+                          pass.GetRenderTargetSize().width);
+      ImGui::SliderFloat("Rotation", &rotation, 0, kPi * 2);
+      ImGui::SliderFloat2("Scale", &scale[0], 0, 3);
+      ImGui::SliderFloat2("Skew", &skew[0], -3, 3);
+    }
     ImGui::End();
 
     auto blend = FilterContents::MakeBlend(
         Entity::BlendMode::kPlus, FilterInput::Make({boston, bridge, bridge}));
 
     auto blur = FilterContents::MakeGaussianBlur(
-        FilterInput::Make(blend), blur_amount[0], blur_amount[1]);
+        FilterInput::Make(blend), blur_amount[0], blur_amount[1],
+        blur_styles[selected_blur_style]);
 
     ISize input_size = boston->GetSize();
     auto rect = Rect(-Point(input_size) / 2, Size(input_size));

impeller/entity/shaders/gaussian_blur.frag

@@ -5,16 +5,21 @@
 // 1D (directional) gaussian blur.
 //
 // Paths for future optimization:
-//   * Remove the uv bounds check branch in SampleColor by adding optional
+//   * Remove the uv bounds multiplier in SampleColor by adding optional
 //     support for SamplerAddressMode::ClampToBorder in the texture sampler.
 //   * Sample from higher mipmap levels when the blur radius is high enough.
 
 uniform sampler2D texture_sampler;
+uniform sampler2D alpha_mask_sampler;
 
 in vec2 v_texture_coords;
+in vec2 v_src_texture_coords;
 in vec2 v_texture_size;
 in vec2 v_blur_direction;
 in float v_blur_radius;
+in float v_src_factor;
+in float v_inner_blur_factor;
+in float v_outer_blur_factor;
 
 out vec4 frag_color;
 
@@ -27,21 +32,27 @@ float Gaussian(float x) {
 }
 
 // Emulate SamplerAddressMode::ClampToBorder.
-vec4 SampleWithBorder(vec2 uv) {
-  if (uv.x > 0 && uv.y > 0 && uv.x < 1 && uv.y < 1) {
-    return texture(texture_sampler, uv);
-  }
-  return vec4(0);
+vec4 SampleWithBorder(sampler2D tex, vec2 uv) {
+  float within_bounds = float(uv.x >= 0 && uv.y >= 0 && uv.x < 1 && uv.y < 1);
+  return texture(tex, uv) * within_bounds;
 }
 
 void main() {
   vec4 total = vec4(0);
   float total_gaussian = 0;
+  vec2 blur_uv_offset = v_blur_direction / v_texture_size;
   for (float i = -v_blur_radius; i <= v_blur_radius; i++) {
     float gaussian = Gaussian(i);
     total_gaussian += gaussian;
-    total += gaussian * SampleWithBorder(v_texture_coords +
-                                         v_blur_direction * i / v_texture_size);
+    total += gaussian * SampleWithBorder(texture_sampler,
+                                         v_texture_coords + blur_uv_offset * i);
   }
-  frag_color = total / total_gaussian;
+
+  vec4 blur_color = total / total_gaussian;
+
+  vec4 src_color = SampleWithBorder(alpha_mask_sampler, v_src_texture_coords);
+  float blur_factor = v_inner_blur_factor * float(src_color.a > 0) +
+                      v_outer_blur_factor * float(src_color.a == 0);
+
+  frag_color = blur_color * blur_factor + src_color * v_src_factor;
 }

impeller/entity/shaders/gaussian_blur.vert

@@ -5,23 +5,37 @@
 uniform FrameInfo {
   mat4 mvp;
   vec2 texture_size;
+
   vec2 blur_direction;
   float blur_radius;
+
+  float src_factor;
+  float inner_blur_factor;
+  float outer_blur_factor;
 }
 frame_info;
 
 in vec2 vertices;
 in vec2 texture_coords;
+in vec2 src_texture_coords;
 
 out vec2 v_texture_coords;
+out vec2 v_src_texture_coords;
 out vec2 v_texture_size;
 out vec2 v_blur_direction;
 out float v_blur_radius;
+out float v_src_factor;
+out float v_inner_blur_factor;
+out float v_outer_blur_factor;
 
 void main() {
   gl_Position = frame_info.mvp * vec4(vertices, 0.0, 1.0);
   v_texture_coords = texture_coords;
+  v_src_texture_coords = src_texture_coords;
   v_texture_size = frame_info.texture_size;
   v_blur_direction = frame_info.blur_direction;
   v_blur_radius = frame_info.blur_radius;
+  v_src_factor = frame_info.src_factor;
+  v_inner_blur_factor = frame_info.inner_blur_factor;
+  v_outer_blur_factor = frame_info.outer_blur_factor;
 }