95696d09bc
The code that computes and inverts the shutter CDF had some issues that caused the result to be asymmetric, this tweaks it to be more robust and produce symmetric outputs for symmetric inputs.
65 lines
2.0 KiB
C++
65 lines
2.0 KiB
C++
/* SPDX-License-Identifier: Apache-2.0
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* Copyright 2011-2022 Blender Foundation */
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#ifndef __UTIL_MATH_CDF_H__
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#define __UTIL_MATH_CDF_H__
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#include "util/algorithm.h"
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#include "util/math.h"
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#include "util/vector.h"
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CCL_NAMESPACE_BEGIN
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/* Evaluate CDF of a given functor with given range and resolution. */
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template<typename Functor>
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void util_cdf_evaluate(
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const int resolution, const float from, const float to, Functor functor, vector<float> &cdf)
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{
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const int cdf_count = resolution + 1;
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const float range = to - from;
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cdf.resize(cdf_count);
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cdf[0] = 0.0f;
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/* Actual CDF evaluation. */
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for (int i = 0; i < resolution; ++i) {
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float x = from + range * (float)i / (resolution - 1);
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float y = functor(x);
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cdf[i + 1] = cdf[i] + fabsf(y);
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}
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/* Normalize the CDF. */
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float fac = (cdf[resolution] == 0.0f) ? 0.0f : 1.0f / cdf[resolution];
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for (int i = 0; i <= resolution; i++) {
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cdf[i] *= fac;
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}
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cdf[resolution] = 1.0f;
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}
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/* Invert pre-calculated CDF function. */
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void util_cdf_invert(const int resolution,
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const float from,
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const float to,
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const vector<float> &cdf,
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const bool make_symmetric,
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vector<float> &inv_cdf);
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/* Evaluate inverted CDF of a given functor with given range and resolution. */
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template<typename Functor>
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void util_cdf_inverted(const int resolution,
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const float from,
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const float to,
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Functor functor,
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const bool make_symmetric,
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vector<float> &inv_cdf)
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{
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vector<float> cdf;
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/* There is no much smartness going around lower resolution for the CDF table,
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* this just to match the old code from pixel filter so it all stays exactly
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* the same and no regression tests are failed.
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*/
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util_cdf_evaluate(resolution - 1, from, to, functor, cdf);
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util_cdf_invert(resolution, from, to, cdf, make_symmetric, inv_cdf);
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}
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CCL_NAMESPACE_END
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#endif /* __UTIL_MATH_H_CDF__ */
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