EVOLUTION-MANAGER

Edit File: tif_float.c

/******************************************************************************
 * $Id: tif_float.c 21102 2010-11-08 20:47:38Z rouault $
 *
 * Project:  GeoTIFF Driver
 * Purpose:  Floating point conversion functions. Convert 16- and 24-bit
 *           floating point numbers into the 32-bit IEEE 754 compliant ones.
 * Author:   Andrey Kiselev, dron@remotesensing.org
 *
 ******************************************************************************
 * Copyright (c) 2005, Andrey Kiselev <dron@remotesensing.org>
 *
 * This code is based on the code from OpenEXR project with the following
 * copyright:
 * 
 * Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
 * Digital Ltd. LLC
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * *       Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * *       Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 * *       Neither the name of Industrial Light & Magic nor the names of
 * its contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

#include "tif_float.h"

/************************************************************************/
/*                           HalfToFloat()                              */
/*                                                                      */
/*  16-bit floating point number to 32-bit one.                         */
/************************************************************************/

GUInt32 HalfToFloat( GUInt16 iHalf )
{

GUInt32 iSign =     (iHalf >> 15) & 0x00000001;
    GUInt32 iExponent = (iHalf >> 10) & 0x0000001f;
    GUInt32 iMantissa = iHalf         & 0x000003ff;

if (iExponent == 0)
    {
	if (iMantissa == 0)
	{
/* -------------------------------------------------------------------- */
/*	Plus or minus zero.			                        */
/* -------------------------------------------------------------------- */

return iSign << 31;
	}
	else
	{
/* -------------------------------------------------------------------- */
/*	Denormalized number -- renormalize it.			        */
/* -------------------------------------------------------------------- */

while (!(iMantissa & 0x00000400))
	    {
		iMantissa <<= 1;
		iExponent -=  1;
	    }

iExponent += 1;
	    iMantissa &= ~0x00000400;
	}
    }
    else if (iExponent == 31)
    {
	if (iMantissa == 0)
	{
/* -------------------------------------------------------------------- */
/*	 Positive or negative infinity.			                */
/* -------------------------------------------------------------------- */

return (iSign << 31) | 0x7f800000;
	}
	else
	{
/* -------------------------------------------------------------------- */
/*	 NaN -- preserve sign and significand bits.	                */
/* -------------------------------------------------------------------- */

return (iSign << 31) | 0x7f800000 | (iMantissa << 13);
	}
    }

/* -------------------------------------------------------------------- */
/*	 Normalized number.			                        */
/* -------------------------------------------------------------------- */

iExponent = iExponent + (127 - 15);
    iMantissa = iMantissa << 13;

/* -------------------------------------------------------------------- */
/*	 Assemble sign, exponent and mantissa.			        */
/* -------------------------------------------------------------------- */

return (iSign << 31) | (iExponent << 23) | iMantissa;
}

/************************************************************************/
/*                           TripleToFloat()                            */
/*                                                                      */
/*  24-bit floating point number to 32-bit one.                         */
/************************************************************************/

GUInt32 TripleToFloat( GUInt32 iTriple )
{

GUInt32 iSign       = (iTriple >> 23) & 0x00000001;
    GUInt32 iExponent   = (iTriple >> 16) & 0x0000007f;
    GUInt32 iMantissa   = iTriple         & 0x0000ffff;

while (!(iMantissa & 0x00002000))
	    {
		iMantissa <<= 1;
		iExponent -=  1;
	    }

iExponent += 1;
	    iMantissa &= ~0x00002000;
	}
    }
    else if (iExponent == 127)
    {
	if (iMantissa == 0)
	{
/* -------------------------------------------------------------------- */
/*	 Positive or negative infinity.			                */
/* -------------------------------------------------------------------- */

return (iSign << 31) | 0x7f800000 | (iMantissa << 7);
	}
    }

iExponent = iExponent + (127 - 63);
    iMantissa = iMantissa << 7;

return (iSign << 31) | (iExponent << 23) | iMantissa;
}