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21211cd63b
Using an approximated pow function improves the conversion speed of LAB images by more than 50% without an appreciable visual difference.
36 lines
791 B
C
36 lines
791 B
C
/*
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Approximated math functions used into conversions.
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SPDX-FileCopyrightText: Edward Kmett
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SPDX-FileCopyrightText: 2023 Mirco Miranda <mircomir@outlook.com>
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SPDX-License-Identifier: BSD-3-Clause
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*/
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#ifndef FASTMATH_P_H
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#define FASTMATH_P_H
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#include <QtGlobal>
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/*!
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* \brief fastPow
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* Based on Edward Kmett code released into the public domain.
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* See also: https://github.com/ekmett/approximate
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*/
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inline double fastPow(double x, double y)
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{
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union {
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double d;
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qint32 i[2];
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} u = {x};
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#if Q_BYTE_ORDER == Q_LITTLE_ENDIAN
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u.i[1] = qint32(y * (u.i[1] - 1072632447) + 1072632447);
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u.i[0] = 0;
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#else // never tested
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u.i[0] = qint32(y * (u.i[0] - 1072632447) + 1072632447);
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u.i[1] = 0;
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#endif
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return u.d;
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}
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#endif // FASTMATH_P_H
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