9d152e9c66
Add helper functions for converting between floating point and fixed point numbers. Also add tests for them. Signed-off-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
67 lines
1.9 KiB
C++
67 lines
1.9 KiB
C++
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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/*
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* Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com>
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*
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* Miscellaneous utility functions specific to rkisp1
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*/
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#pragma once
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#include <cmath>
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#include <limits>
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#include <type_traits>
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namespace libcamera {
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namespace ipa::rkisp1::utils {
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#ifndef __DOXYGEN__
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template<unsigned int I, unsigned int F, typename R, typename T,
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std::enable_if_t<std::is_integral_v<R> &&
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std::is_floating_point_v<T>> * = nullptr>
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#else
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template<unsigned int I, unsigned int F, typename R, typename T>
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#endif
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constexpr R floatingToFixedPoint(T number)
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{
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static_assert(sizeof(int) >= sizeof(R));
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static_assert(I + F <= sizeof(R) * 8);
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/*
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* The intermediate cast to int is needed on arm platforms to properly
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* cast negative values. See
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* https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/
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*/
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R mask = (1 << (F + I)) - 1;
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R frac = static_cast<R>(static_cast<int>(std::round(number * (1 << F)))) & mask;
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return frac;
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}
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#ifndef __DOXYGEN__
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template<unsigned int I, unsigned int F, typename R, typename T,
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std::enable_if_t<std::is_floating_point_v<R> &&
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std::is_integral_v<T>> * = nullptr>
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#else
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template<unsigned int I, unsigned int F, typename R, typename T>
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#endif
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constexpr R fixedToFloatingPoint(T number)
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{
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static_assert(sizeof(int) >= sizeof(T));
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static_assert(I + F <= sizeof(T) * 8);
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/*
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* Recreate the upper bits in case of a negative number by shifting the sign
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* bit from the fixed point to the first bit of the unsigned and then right shifting
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* by the same amount which keeps the sign bit in place.
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* This can be optimized by the compiler quite well.
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*/
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int remaining_bits = sizeof(int) * 8 - (I + F);
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int t = static_cast<int>(static_cast<unsigned>(number) << remaining_bits) >> remaining_bits;
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return static_cast<R>(t) / static_cast<R>(1 << F);
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}
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} /* namespace ipa::rkisp1::utils */
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} /* namespace libcamera */
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