Add Chromium-only Blender WebEngine parity work

blender-5.2.0/intern/cycles/util/math_cdf.h

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+/* SPDX-FileCopyrightText: 2011-2022 Blender Foundation
+ *
+ * SPDX-License-Identifier: Apache-2.0 */
+
+#pragma once
+
+#include "util/math_base.h"
+#include "util/vector.h"
+
+CCL_NAMESPACE_BEGIN
+
+/* Evaluate CDF of a given functor with given range and resolution. */
+template<typename Functor>
+void util_cdf_evaluate(
+    const int resolution, const float from, const float to, Functor functor, vector<float> &cdf)
+{
+  const int cdf_count = resolution + 1;
+  const float range = to - from;
+  cdf.resize(cdf_count);
+  cdf[0] = 0.0f;
+  /* Actual CDF evaluation. */
+  for (int i = 0; i < resolution; ++i) {
+    float x = from + range * (float)i / (resolution - 1);
+    float y = functor(x);
+    cdf[i + 1] = cdf[i] + fabsf(y);
+  }
+  /* Normalize the CDF. */
+  const float fac = (cdf[resolution] == 0.0f) ? 0.0f : 1.0f / cdf[resolution];
+  for (int i = 0; i <= resolution; i++) {
+    cdf[i] *= fac;
+  }
+  cdf[resolution] = 1.0f;
+}
+
+/* Invert pre-calculated CDF function. */
+void util_cdf_invert(const int resolution,
+                     const float from,
+                     const float to,
+                     const vector<float> &cdf,
+                     const bool make_symmetric,
+                     vector<float> &inv_cdf);
+
+/* Evaluate inverted CDF of a given functor with given range and resolution. */
+template<typename Functor>
+void util_cdf_inverted(const int resolution,
+                       const float from,
+                       const float to,
+                       Functor functor,
+                       const bool make_symmetric,
+                       vector<float> &inv_cdf)
+{
+  vector<float> cdf;
+  /* There is no much smartness going around lower resolution for the CDF table,
+   * this just to match the old code from pixel filter so it all stays exactly
+   * the same and no regression tests are failed.
+   */
+  util_cdf_evaluate(resolution - 1, from, to, functor, cdf);
+  util_cdf_invert(resolution, from, to, cdf, make_symmetric, inv_cdf);
+}
+
+CCL_NAMESPACE_END