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authorPaul Elder <paul.elder@ideasonboard.com>2024-03-27 17:54:49 +0900
committerPaul Elder <paul.elder@ideasonboard.com>2024-05-31 17:12:48 +0900
commit9d152e9c66c1094a482e704d95965078a0fe2cf3 (patch)
treeb2fb40ead282da27a96586ef318a2482225282dc /src/ipa/rkisp1/utils.h
parentc79fa47aac9b38865dab5e9f29030903bf460c46 (diff)
ipa: rkisp1: Add a helper to convert floating-point to fixed-point
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>
Diffstat (limited to 'src/ipa/rkisp1/utils.h')
-rw-r--r--src/ipa/rkisp1/utils.h66
1 files changed, 66 insertions, 0 deletions
diff --git a/src/ipa/rkisp1/utils.h b/src/ipa/rkisp1/utils.h
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Paul Elder <paul.elder@ideasonboard.com>
+ *
+ * Miscellaneous utility functions specific to rkisp1
+ */
+
+#pragma once
+
+#include <cmath>
+#include <limits>
+#include <type_traits>
+
+namespace libcamera {
+
+namespace ipa::rkisp1::utils {
+
+#ifndef __DOXYGEN__
+template<unsigned int I, unsigned int F, typename R, typename T,
+ std::enable_if_t<std::is_integral_v<R> &&
+ std::is_floating_point_v<T>> * = nullptr>
+#else
+template<unsigned int I, unsigned int F, typename R, typename T>
+#endif
+constexpr R floatingToFixedPoint(T number)
+{
+ static_assert(sizeof(int) >= sizeof(R));
+ static_assert(I + F <= sizeof(R) * 8);
+
+ /*
+ * The intermediate cast to int is needed on arm platforms to properly
+ * cast negative values. See
+ * https://embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/
+ */
+ R mask = (1 << (F + I)) - 1;
+ R frac = static_cast<R>(static_cast<int>(std::round(number * (1 << F)))) & mask;
+
+ return frac;
+}
+
+#ifndef __DOXYGEN__
+template<unsigned int I, unsigned int F, typename R, typename T,
+ std::enable_if_t<std::is_floating_point_v<R> &&
+ std::is_integral_v<T>> * = nullptr>
+#else
+template<unsigned int I, unsigned int F, typename R, typename T>
+#endif
+constexpr R fixedToFloatingPoint(T number)
+{
+ static_assert(sizeof(int) >= sizeof(T));
+ static_assert(I + F <= sizeof(T) * 8);
+
+ /*
+ * Recreate the upper bits in case of a negative number by shifting the sign
+ * bit from the fixed point to the first bit of the unsigned and then right shifting
+ * by the same amount which keeps the sign bit in place.
+ * This can be optimized by the compiler quite well.
+ */
+ int remaining_bits = sizeof(int) * 8 - (I + F);
+ int t = static_cast<int>(static_cast<unsigned>(number) << remaining_bits) >> remaining_bits;
+ return static_cast<R>(t) / static_cast<R>(1 << F);
+}
+
+} /* namespace ipa::rkisp1::utils */
+
+} /* namespace libcamera */