1 files changed, 141 insertions, 3 deletions

diff --git a/source/blender/nodes/composite/nodes/node_composite_levels.cc b/source/blender/nodes/composite/nodes/node_composite_levels.cc
index a4fe1f33813..4c901372b9f 100644
--- a/source/blender/nodes/composite/nodes/node_composite_levels.cc
+++ b/source/blender/nodes/composite/nodes/node_composite_levels.cc
@@ -5,9 +5,18 @@
  * \ingroup cmpnodes
  */
 
+#include <cmath>
+
+#include "BLI_assert.h"
+#include "BLI_math_vec_types.hh"
+#include "BLI_math_vector.hh"
+
 #include "UI_interface.h"
 #include "UI_resources.h"
 
+#include "IMB_colormanagement.h"
+
+#include "COM_algorithm_parallel_reduction.hh"
 #include "COM_node_operation.hh"
 
 #include "node_composite_util.hh"
@@ -18,7 +27,9 @@ namespace blender::nodes::node_composite_levels_cc {
 
 static void cmp_node_levels_declare(NodeDeclarationBuilder &b)
 {
-  b.add_input<decl::Color>(N_("Image")).default_value({0.0f, 0.0f, 0.0f, 1.0f});
+  b.add_input<decl::Color>(N_("Image"))
+      .default_value({0.0f, 0.0f, 0.0f, 1.0f})
+      .compositor_domain_priority(0);
   b.add_output<decl::Float>(N_("Mean"));
   b.add_output<decl::Float>(N_("Std Dev"));
 }
@@ -36,13 +47,140 @@ static void node_composit_buts_view_levels(uiLayout *layout, bContext * /*C*/, P
 using namespace blender::realtime_compositor;
 
 class LevelsOperation : public NodeOperation {
+ private:
+  constexpr static float luminance_coefficients_bt709_[3] = {0.2126f, 0.7152f, 0.0722f};
+
  public:
   using NodeOperation::NodeOperation;
 
   void execute() override
   {
-    get_result("Mean").allocate_invalid();
-    get_result("Std Dev").allocate_invalid();
+    if (get_input("Image").is_single_value()) {
+      execute_single_value();
+      return;
+    }
+
+    const float mean = compute_mean();
+
+    Result &mean_result = get_result("Mean");
+    if (mean_result.should_compute()) {
+      mean_result.allocate_single_value();
+      mean_result.set_float_value(mean);
+    }
+
+    Result &standard_deviation_result = get_result("Std Dev");
+    if (standard_deviation_result.should_compute()) {
+      const float standard_deviation = compute_standard_deviation(mean);
+      standard_deviation_result.allocate_single_value();
+      standard_deviation_result.set_float_value(standard_deviation);
+    }
+  }
+
+  void execute_single_value()
+  {
+    Result &standard_deviation_result = get_result("Std Dev");
+    if (standard_deviation_result.should_compute()) {
+      standard_deviation_result.allocate_single_value();
+      standard_deviation_result.set_float_value(0.0f);
+    }
+
+    Result &mean_result = get_result("Mean");
+    if (!mean_result.should_compute()) {
+      return;
+    }
+
+    mean_result.allocate_single_value();
+    const float3 input = float3(get_input("Image").get_color_value());
+
+    switch (get_channel()) {
+      case CMP_NODE_LEVLES_RED:
+        mean_result.set_float_value(input.x);
+        break;
+      case CMP_NODE_LEVLES_GREEN:
+        mean_result.set_float_value(input.y);
+        break;
+      case CMP_NODE_LEVLES_BLUE:
+        mean_result.set_float_value(input.z);
+        break;
+      case CMP_NODE_LEVLES_LUMINANCE_BT709:
+        mean_result.set_float_value(math::dot(input, float3(luminance_coefficients_bt709_)));
+        break;
+      case CMP_NODE_LEVLES_LUMINANCE: {
+        float luminance_coefficients[3];
+        IMB_colormanagement_get_luminance_coefficients(luminance_coefficients);
+        mean_result.set_float_value(math::dot(input, float3(luminance_coefficients)));
+        break;
+      }
+      default:
+        BLI_assert_unreachable();
+        break;
+    }
+  }
+
+  float compute_mean()
+  {
+    const Result &input = get_input("Image");
+    return compute_sum() / (input.domain().size.x * input.domain().size.y);
+  }
+
+  float compute_sum()
+  {
+    const Result &input = get_input("Image");
+    switch (get_channel()) {
+      case CMP_NODE_LEVLES_RED:
+        return sum_red(context(), input.texture());
+      case CMP_NODE_LEVLES_GREEN:
+        return sum_green(context(), input.texture());
+      case CMP_NODE_LEVLES_BLUE:
+        return sum_blue(context(), input.texture());
+      case CMP_NODE_LEVLES_LUMINANCE_BT709:
+        return sum_luminance(context(), input.texture(), float3(luminance_coefficients_bt709_));
+      case CMP_NODE_LEVLES_LUMINANCE: {
+        float luminance_coefficients[3];
+        IMB_colormanagement_get_luminance_coefficients(luminance_coefficients);
+        return sum_luminance(context(), input.texture(), float3(luminance_coefficients));
+      }
+      default:
+        BLI_assert_unreachable();
+        return 0.0f;
+    }
+  }
+
+  float compute_standard_deviation(float mean)
+  {
+    const Result &input = get_input("Image");
+    const float sum = compute_sum_squared_difference(mean);
+    return std::sqrt(sum / (input.domain().size.x * input.domain().size.y));
+  }
+
+  float compute_sum_squared_difference(float subtrahend)
+  {
+    const Result &input = get_input("Image");
+    switch (get_channel()) {
+      case CMP_NODE_LEVLES_RED:
+        return sum_red_squared_difference(context(), input.texture(), subtrahend);
+      case CMP_NODE_LEVLES_GREEN:
+        return sum_green_squared_difference(context(), input.texture(), subtrahend);
+      case CMP_NODE_LEVLES_BLUE:
+        return sum_blue_squared_difference(context(), input.texture(), subtrahend);
+      case CMP_NODE_LEVLES_LUMINANCE_BT709:
+        return sum_luminance_squared_difference(
+            context(), input.texture(), float3(luminance_coefficients_bt709_), subtrahend);
+      case CMP_NODE_LEVLES_LUMINANCE: {
+        float luminance_coefficients[3];
+        IMB_colormanagement_get_luminance_coefficients(luminance_coefficients);
+        return sum_luminance_squared_difference(
+            context(), input.texture(), float3(luminance_coefficients), subtrahend);
+      }
+      default:
+        BLI_assert_unreachable();
+        return 0.0f;
+    }
+  }
+
+  CMPNodeLevelsChannel get_channel()
+  {
+    return static_cast<CMPNodeLevelsChannel>(bnode().custom1);
   }
 };