The filter is used to reduce noise while preserving edges. It can be used to create a cartoon effect from photorealistic images.

The idea is to offer two modes:
1) Calssic aka isotropic kuwahara filter: simple and faster computation. Algorithm splits an area around a single pixel in four parts and selects the mean of the region with the lowest standard deviation
2) Anisotropic Kuwahara filter: improve the classical approach by considering the direction of structures of regions

This patch implements the isotropic approach as a single threaded operation for the full-frame compositor

@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2011 Blender Foundation. */

@@ -0,0 +9,4 @@
+{
+  this->add_input_socket(DataType::Color);
+  this->add_output_socket(DataType::Color);
+  this->set_kernel_size(4.4f);

@@ -0,0 +32,4 @@
+  float input_value[4];
+  image_reader_->read_sampled(input_value, x, y, sampler);
+
+  output[0] = input_value[0] + 1.0;

@@ -0,0 +80,4 @@
+
+          int xx = x + dx;
+          int yy = y + dy;
+          if (xx >= 0 && yy >= 0 && xx < area.xmax && yy < area.ymax) {

@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2011 Blender Foundation. */

@@ -69,1 +70,4 @@
 
+void FastGaussianBlurOperation::set_size(int size_x, int size_y)
+{
+  // todo: there should be a better way to use the operation without knowing specifics of the blur

@@ -0,0 +19,4 @@
+
+  this->add_output_socket(DataType::Color);
+  // output for debug
+  // todo: remove

@@ -0,0 +44,4 @@
+                                                         float y,
+                                                         PixelSampler sampler)
+{
+  /* Not implemented */

@@ -0,0 +33,4 @@
+                                                     float y,
+                                                     PixelSampler sampler)
+{
+  /* Not implemented */

@@ -0,0 +6,4 @@
+ */
+
+#include "COM_node_operation.hh"
+//#include "node_composite_util.hh"

@@ -9245,0 +9256,4 @@
+
+  prop = RNA_def_property(srna, "size", PROP_INT, PROP_NONE);
+  RNA_def_property_int_sdna(prop, NULL, "size");
+  RNA_def_property_ui_range(prop, 4, 50, 1, -1);

@@ -0,0 +102,4 @@
+        if (xx < 0) {
+          xx = 0;
+        }
+        if (xx >= this->get_width()) {

@@ -0,0 +115,4 @@
+        double ddx2 = (double)dx2;
+        double ddy2 = (double)dy2;
+        double theta = atan2(ddy2, ddx2) + M_PI;
+        int t = static_cast<int>(floor(theta / angle)) % n_div_;

@@ -0,0 +135,4 @@
+    double de = 0.0;
+    double nu = 0.0;
+    for (int i = 0; i < n_div_; i++) {
+      mean[i] = weight[i] != 0 ? mean[i] / weight[i] : 0.0;

@@ -0,0 +24,4 @@
+      converter.add_operation(operation);
+      converter.map_input_socket(get_input_socket(0), operation->get_input_socket(0));
+      converter.map_output_socket(get_output_socket(0), operation->get_output_socket());
+    } break;

@@ -0,0 +231,4 @@
+
+    for (int ch = 0; ch < 3; ch++) {
+
+      Vector<double> mean(n_div_, 0.0f);

@@ -0,0 +251,4 @@
+          int xx = x + dx2;
+          int yy = y + dy2;
+
+          /* Clamp image to avoid artefacts at borders. */

@@ -0,0 +3,4 @@
+
+#include "COM_KuwaharaClassicOperation.h"
+
+extern "C" {