Add image filter examples.

Author: chuckyount

src/stencils/ImageFilters.cpp

@@ -0,0 +1,125 @@
+/*****************************************************************************
+
+YASK: Yet Another Stencil Kit
+Copyright (c) 2014-2024, Intel Corporation
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to
+deal in the Software without restriction, including without limitation the
+rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+sell copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+* The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+IN THE SOFTWARE.
+
+*****************************************************************************/
+
+// Example stencil equations for 2D image filtering.
+
+// YASK stencil solution(s) in this file will be integrated into the YASK compiler utility.
+#include "yask_compiler_api.hpp"
+using namespace std;
+using namespace yask;
+
+// Create an anonymous namespace to ensure that types are local.
+namespace {
+
+    using yn=yc_number_node_ptr;
+    using yb=yc_bool_node_ptr;
+
+    // A simple smoothing filter where each pixel is updated with the
+    // average value of its neighbors.
+    class BoxFilter : public yc_solution_with_radius_base {
+
+    protected:
+        // Indices & dimensions.
+        MAKE_STEP_INDEX(n);           // step dim.
+        MAKE_DOMAIN_INDEX(x);         // spatial dim.
+        MAKE_DOMAIN_INDEX(y);         // spatial dim.
+
+        // Vars.
+        MAKE_VAR(A, n, x, y);
+        
+    public:
+        BoxFilter(string name="box_filter", int radius=2) :
+            yc_solution_with_radius_base(name, radius) { }
+
+        // Define equation at n+1 based on values at n.
+        virtual void define() {
+            auto r = get_radius();
+
+            // RHS of expression being created.
+            yn v;
+
+            // Add points in square from step n.
+            for (int i = -r; i <= r; i++)
+                for (int j = -r; j <= r; j++)
+                    v += A(n, x+i, y+j);
+
+            // Average by dividing by number of points
+            // in square.
+            v /= r * r;
+        
+            // Define the value at n+1 to be expression v.
+            A(n+1, x, y) EQUALS v;
+        }
+    };
+    REGISTER_SOLUTION(BoxFilter);
+
+    // Isotropic Gaussian.
+    // TODO: update to parameterize sigma (or perhaps parameterize
+    // radius and determine good sigma value from requested radius).
+    class GaussianFilter : public yc_solution_base {
+
+    protected:
+        // Indices & dimensions.
+        MAKE_STEP_INDEX(n);           // step dim.
+        MAKE_DOMAIN_INDEX(x);         // spatial dim.
+        MAKE_DOMAIN_INDEX(y);         // spatial dim.
+
+        // Vars.
+        MAKE_VAR(A, n, x, y);
+        
+    public:
+        GaussianFilter(string name="gaussian_filter") :
+            yc_solution_base(name) { }
+
+        // Define equation at n+1 based on values at n.
+        virtual void define() {
+
+            // G(x, y) = exp(-(x^2 + y^2) / (2 * sigma^2)) / (2 * pi * sigma^2).
+            // For the given coefficients, sigma = 1.0.
+            // See https://homepages.inf.ed.ac.uk/rbf/HIPR2/gsmooth.htm
+
+            // RHS of expression being created.
+            yn v;
+
+            // Add points in square from step n.
+            double coeff[5][5] = { { 1.,  4.,  7.,  4., 1. },
+                                   { 4., 16., 26., 16., 4. },
+                                   { 7., 26., 41., 26., 7. },
+                                   { 4., 16., 26., 16., 4. },
+                                   { 1.,  4.,  7.,  4., 1. } };
+            double sum = 273.;
+            for (int i = -2; i <= 2; i++)
+                for (int j = -2; j <= 2; j++) {
+                    double c = coeff[i+2][j+2] / sum;
+                    v += A(n, x+i, y+j) * c;
+                }
+        
+            // Define the value at n+1 to be expression v.
+            A(n+1, x, y) EQUALS v;
+        }
+    };
+    REGISTER_SOLUTION(GaussianFilter);
+
+}; // namespace.