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193 lines
7.2 KiB
C
193 lines
7.2 KiB
C
/******************************************************************************
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* $Id: tif_float.c 10645 2007-01-18 02:22:39Z warmerdam $
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*
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* Project: GeoTIFF Driver
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* Purpose: Floating point conversion functions. Convert 16- and 24-bit
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* floating point numbers into the 32-bit IEEE 754 compliant ones.
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* Author: Andrey Kiselev, dron@remotesensing.org
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*
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******************************************************************************
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* Copyright (c) 2005, Andrey Kiselev <dron@remotesensing.org>
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*
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* This code is based on the code from OpenEXR project with the following
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* copyright:
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*
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* Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
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* Digital Ltd. LLC
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following disclaimer
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* in the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Industrial Light & Magic nor the names of
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* its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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#include "libgeotiff/port/cpl_port.h"
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/************************************************************************/
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/* HalfToFloat() */
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/* */
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/* 16-bit floating point number to 32-bit one. */
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/************************************************************************/
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GUInt32 HalfToFloat( GUInt16 iHalf )
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{
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GUInt32 iSign = (iHalf >> 15) & 0x00000001;
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GUInt32 iExponent = (iHalf >> 10) & 0x0000001f;
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GUInt32 iMantissa = iHalf & 0x000003ff;
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if (iExponent == 0)
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{
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if (iMantissa == 0)
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{
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/* -------------------------------------------------------------------- */
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/* Plus or minus zero. */
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/* -------------------------------------------------------------------- */
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return iSign << 31;
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}
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else
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{
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/* -------------------------------------------------------------------- */
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/* Denormalized number -- renormalize it. */
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/* -------------------------------------------------------------------- */
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while (!(iMantissa & 0x00000400))
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{
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iMantissa <<= 1;
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iExponent -= 1;
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}
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iExponent += 1;
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iMantissa &= ~0x00000400;
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}
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}
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else if (iExponent == 31)
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{
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if (iMantissa == 0)
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{
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/* -------------------------------------------------------------------- */
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/* Positive or negative infinity. */
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/* -------------------------------------------------------------------- */
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return (iSign << 31) | 0x7f800000;
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}
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else
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{
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/* -------------------------------------------------------------------- */
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/* NaN -- preserve sign and significand bits. */
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/* -------------------------------------------------------------------- */
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return (iSign << 31) | 0x7f800000 | (iMantissa << 13);
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}
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}
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/* -------------------------------------------------------------------- */
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/* Normalized number. */
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/* -------------------------------------------------------------------- */
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iExponent = iExponent + (127 - 15);
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iMantissa = iMantissa << 13;
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/* -------------------------------------------------------------------- */
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/* Assemble sign, exponent and mantissa. */
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/* -------------------------------------------------------------------- */
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return (iSign << 31) | (iExponent << 23) | iMantissa;
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}
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/************************************************************************/
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/* TripleToFloat() */
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/* */
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/* 24-bit floating point number to 32-bit one. */
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/************************************************************************/
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GUInt32 TripleToFloat( GUInt32 iTriple )
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{
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GUInt32 iSign = (iTriple >> 23) & 0x00000001;
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GUInt32 iExponent = (iTriple >> 16) & 0x0000007f;
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GUInt32 iMantissa = iTriple & 0x0000ffff;
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if (iExponent == 0)
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{
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if (iMantissa == 0)
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{
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/* -------------------------------------------------------------------- */
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/* Plus or minus zero. */
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/* -------------------------------------------------------------------- */
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return iSign << 31;
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}
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else
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{
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/* -------------------------------------------------------------------- */
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/* Denormalized number -- renormalize it. */
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/* -------------------------------------------------------------------- */
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while (!(iMantissa & 0x00002000))
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{
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iMantissa <<= 1;
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iExponent -= 1;
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}
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iExponent += 1;
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iMantissa &= ~0x00002000;
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}
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}
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else if (iExponent == 127)
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{
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if (iMantissa == 0)
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{
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/* -------------------------------------------------------------------- */
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/* Positive or negative infinity. */
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/* -------------------------------------------------------------------- */
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return (iSign << 31) | 0x7f800000;
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}
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else
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{
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/* -------------------------------------------------------------------- */
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/* NaN -- preserve sign and significand bits. */
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/* -------------------------------------------------------------------- */
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return (iSign << 31) | 0x7f800000 | (iMantissa << 7);
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}
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}
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/* -------------------------------------------------------------------- */
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/* Normalized number. */
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/* -------------------------------------------------------------------- */
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iExponent = iExponent + (127 - 63);
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iMantissa = iMantissa << 7;
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/* -------------------------------------------------------------------- */
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/* Assemble sign, exponent and mantissa. */
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/* -------------------------------------------------------------------- */
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return (iSign << 31) | (iExponent << 23) | iMantissa;
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}
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