imfb44compressor.cpp

image converter source code

///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2006, 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.
//
///////////////////////////////////////////////////////////////////////////


//-----------------------------------------------------------------------------
//
//	class B44Compressor
//
//	This compressor is lossy for HALF channels; the compression rate
//	is fixed at 32/14 (approximately 2.28).  FLOAT and UINT channels
//	are not compressed; their data are preserved exactly.
//
//	Each HALF channel is split into blocks of 4 by 4 pixels.  An
//	uncompressed block occupies 32 bytes, which are re-interpreted
//	as sixteen 16-bit unsigned integers, t[0] ... t[15].  Compression
//	shrinks the block to 14 bytes.  The compressed 14-byte block
//	contains
//
//	 - t[0]
//
//	 - a 6-bit shift value
//
//	 - 15 densely packed 6-bit values, r[0] ... r[14], which are
//         computed by subtracting adjacent pixel values and right-
//	   shifting the differences according to the stored shift value.
//
//	   Differences between adjacent pixels are computed according
//	   to the following diagram:
//
//		 0 -------->  1 -------->  2 -------->  3
//               |     3            7           11
//               |
//               | 0
//               |
//               v 
//		 4 -------->  5 -------->  6 -------->  7
//               |     4            8           12
//               |
//               | 1
//               |
//               v
//		 8 -------->  9 --------> 10 --------> 11
//               |     5            9           13
//               |
//               | 2
//               |
//               v
//		12 --------> 13 --------> 14 --------> 15
//                     6           10           14
//
//	    Here
//
//               5 ---------> 6
//                     8
//
//	    means that r[8] is the difference between t[5] and t[6].
//
//	 - optionally, a 4-by-4 pixel block where all pixels have the
//	   same value can be treated as a special case, where the
//	   compressed block contains only 3 instead of 14 bytes:
//	   t[0], followed by an "impossible" 6-bit shift value and
//	   two padding bits.
//
//	This compressor can handle positive and negative pixel values.
//	NaNs and infinities are replaced with zeroes before compression.
//
//-----------------------------------------------------------------------------

#include <ImfB44Compressor.h>
#include <ImfHeader.h>
#include <ImfChannelList.h>
#include <ImfMisc.h>
#include <ImathFun.h>
#include <ImathBox.h>
#include <Iex.h>
#include <ImfIO.h>
#include <ImfXdr.h>
#include <string.h>
#include <assert.h>
#include <algorithm>

namespace Imf {

using Imath::divp;
using Imath::modp;
using Imath::Box2i;
using Imath::V2i;
using std::min;

namespace {

//
// Lookup tables for
//	y = exp (x / 8)
// and 
//	x = 8 * log (y)
//

#include "b44ExpLogTable.h"


inline void
convertFromLinear (unsigned short s[16])
{
    for (int i = 0; i < 16; ++i)
	s[i] = expTable[s[i]];
}


inline void
convertToLinear (unsigned short s[16])
{
    for (int i = 0; i < 16; ++i)
	s[i] = logTable[s[i]];
}


inline int
shiftAndRound (int x, int shift)
{
    //
    // Compute
    //
    //     y = x * pow (2, -shift),
    //
    // then round y to the nearest integer.
    // In case of a tie, where y is exactly
    // halfway between two integers, round
    // to the even one.
    //

    x <<= 1;
    int a = (1 << shift) - 1;
    shift += 1;
    int b = (x >> shift) & 1;
    return (x + a + b) >> shift;
}


int
pack (const unsigned short s[16],
      unsigned char b[14],
      bool optFlatFields,
      bool exactMax)
{
    //
    // Pack a block of 4 by 4 16-bit pixels (32 bytes) into
    // either 14 or 3 bytes.
    //

    //
    // Integers s[0] ... s[15] represent floating-point numbers
    // in what is essentially a sign-magnitude format.  Convert
    // s[0] .. s[15] into a new set of integers, t[0] ... t[15],
    // such that if t[i] is greater than t[j], the floating-point
    // number that corresponds to s[i] is always greater than
    // the floating-point number that corresponds to s[j].
    //
    // Also, replace any bit patterns that represent NaNs or
    // infinities with bit patterns that represent floating-point
    // zeroes.
    //
    //	bit pattern	floating-point		bit pattern
    //	in s[i]		value			in t[i]
    //
    //  0x7fff		NAN			0x8000
    //  0x7ffe		NAN			0x8000
    //	  ...					  ...
    //  0x7c01		NAN			0x8000
    //  0x7c00		+infinity		0x8000
    //  0x7bff		+HALF_MAX		0xfbff
    //  0x7bfe					0xfbfe
    //  0x7bfd					0xfbfd
    //	  ...					  ...
    //  0x0002		+2 * HALF_MIN		0x8002
    //  0x0001		+HALF_MIN		0x8001
    //  0x0000		+0.0			0x8000
    //  0x8000		-0.0			0x7fff
    //  0x8001		-HALF_MIN		0x7ffe
    //  0x8002		-2 * HALF_MIN		0x7ffd
    //	  ...					  ...
    //  0xfbfd					0x0f02
    //  0xfbfe					0x0401
    //  0xfbff		-HALF_MAX		0x0400
    //  0xfc00		-infinity		0x8000
    //  0xfc01		NAN			0x8000
    //	  ...					  ...
    //  0xfffe		NAN			0x8000
    //  0xffff		NAN			0x8000
    //

    unsigned short t[16];

    for (int i = 0; i < 16; ++i)
    {
	if ((s[i] & 0x7c00) == 0x7c00)
	    t[i] = 0x8000;
	else if (s[i] & 0x8000)
	    t[i] = ~s[i];
	else
	    t[i] = s[i] | 0x8000;
    }
    
    //
    // Find the maximum, tMax, of t[0] ... t[15].
    //

    unsigned short tMax = 0;

    for (int i = 0; i < 16; ++i)
	if (tMax < t[i])
	    tMax = t[i];

    //
    // Compute a set of running differences, r[0] ... r[14]:
    // Find a shift value such that after rounding off the
    // rightmost bits and shifting all differenes are between
    // -32 and +31.  Then bias the differences so that they
    // end up between 0 and 63.
    //

    int shift = -1;
    int d[16];
    int r[15];
    int rMin;
    int rMax;

    const int bias = 0x20;

    do
    {
	shift += 1;

	//
	// Compute absolute differences, d[0] ... d[15],
	// between tMax and t[0] ... t[15].
	//
	// Shift and round the absolute differences.
	//

	for (int i = 0; i < 16; ++i)
	    d[i] = shiftAndRound (tMax - t[i], shift);

	//
	// Convert d[0] .. d[15] into running differences
	//

	r[ 0] = d[ 0] - d[ 4] + bias;
	r[ 1] = d[ 4] - d[ 8] + bias;
	r[ 2] = d[ 8] - d[12] + bias;

	r[ 3] = d[ 0] - d[ 1] + bias;
	r[ 4] = d[ 4] - d[ 5] + bias;
	r[ 5] = d[ 8] - d[ 9] + bias;
	r[ 6] = d[12] - d[13] + bias;

	r[ 7] = d[ 1] - d[ 2] + bias;
	r[ 8] = d[ 5] - d[ 6] + bias;
	r[ 9] = d[ 9] - d[10] + bias;
	r[10] = d[13] - d[14] + bias;

	r[11] = d[ 2] - d[ 3] + bias;
	r[12] = d[ 6] - d[ 7] + bias;
	r[13] = d[10] - d[11] + bias;
	r[14] = d[14] - d[15] + bias;

	rMin = r[0];
	rMax = r[0];

	for (int i = 1; i < 15; ++i)
	{
	    if (rMin > r[i])
		rMin = r[i];

	    if (rMax < r[i])
		rMax = r[i];
	}
    }
    while (rMin < 0 || rMax > 0x3f);

    if (rMin == bias && rMax == bias && optFlatFields)
    {
	//
	// Special case - all pixels have the same value.
	// We encode this in 3 instead of 14 bytes by
	// storing the value 0xfc in the third output byte,
	// which cannot occur in the 14-byte encoding.
	//

	b[0] = (t[0] >> 8);
	b[1] =  t[0];
	b[2] = 0xfc;

	return 3;
    }

    if (exactMax)
    {
	//
	// Adjust t[0] so that the pixel whose value is equal
	// to tMax gets represented as accurately as possible.
	//

	t[0] = tMax - (d[0] << shift);
    }

    //
    // Pack t[0], shift and r[0] ... r[14] into 14 bytes:
    //

    b[ 0] = (t[0] >> 8);
    b[ 1] =  t[0];

    b[ 2] = (unsigned char) ((shift << 2) | (r[ 0] >> 4));
    b[ 3] = (unsigned char) ((r[ 0] << 4) | (r[ 1] >> 2));
    b[ 4] = (unsigned char) ((r[ 1] << 6) |  r[ 2]      );

    b[ 5] = (unsigned char) ((r[ 3] << 2) | (r[ 4] >> 4));
    b[ 6] = (unsigned char) ((r[ 4] << 4) | (r[ 5] >> 2));
    b[ 7] = (unsigned char) ((r[ 5] << 6) |  r[ 6]      );

    b[ 8] = (unsigned char) ((r[ 7] << 2) | (r[ 8] >> 4));
    b[ 9] = (unsigned char) ((r[ 8] << 4) | (r[ 9] >> 2));
    b[10] = (unsigned char) ((r[ 9] << 6) |  r[10]      );

    b[11] = (unsigned char) ((r[11] << 2) | (r[12] >> 4));
    b[12] = (unsigned char) ((r[12] << 4) | (r[13] >> 2));
    b[13] = (unsigned char) ((r[13] << 6) |  r[14]      );

    return 14;
}


inline
void
unpack14 (const unsigned char b[14], unsigned short s[16])
{
    //
    // Unpack a 14-byte block into 4 by 4 16-bit pixels.
    //

    #if defined (DEBUG)
	assert (b[2] != 0xfc);
    #endif

    s[ 0] = (b[0] << 8) | b[1];

    unsigned short shift = (b[ 2] >> 2);
    unsigned short bias = (0x20 << shift);

    s[ 4] = s[ 0] + ((((b[ 2] << 4) | (b[ 3] >> 4)) & 0x3f) << shift) - bias;
    s[ 8] = s[ 4] + ((((b[ 3] << 2) | (b[ 4] >> 6)) & 0x3f) << shift) - bias;
    s[12] = s[ 8] +   ((b[ 4]                       & 0x3f) << shift) - bias;
    
    s[ 1] = s[ 0] +   ((b[ 5] >> 2)                         << shift) - bias;
    s[ 5] = s[ 4] + ((((b[ 5] << 4) | (b[ 6] >> 4)) & 0x3f) << shift) - bias;
    s[ 9] = s[ 8] + ((((b[ 6] << 2) | (b[ 7] >> 6)) & 0x3f) << shift) - bias;
    s[13] = s[12] +   ((b[ 7]                       & 0x3f) << shift) - bias;
    
    s[ 2] = s[ 1] +   ((b[ 8] >> 2)                         << shift) - bias;
    s[ 6] = s[ 5] + ((((b[ 8] << 4) | (b[ 9] >> 4)) & 0x3f) << shift) - bias;
    s[10] = s[ 9] + ((((b[ 9] << 2) | (b[10] >> 6)) & 0x3f) << shift) - bias;
    s[14] = s[13] +   ((b[10]                       & 0x3f) << shift) - bias;
    
    s[ 3] = s[ 2] +   ((b[11] >> 2)                         << shift) - bias;
    s[ 7] = s[ 6] + ((((b[11] << 4) | (b[12] >> 4)) & 0x3f) << shift) - bias;
    s[11] = s[10] + ((((b[12] << 2) | (b[13] >> 6)) & 0x3f) << shift) - bias;
    s[15] = s[14] +   ((b[13]                       & 0x3f) << shift) - bias;

    for (int i = 0; i < 16; ++i)
    {
	if (s[i] & 0x8000)
	    s[i] &= 0x7fff;
	else
	    s[i] = ~s[i];
    }
}


inline
void
unpack3 (const unsigned char b[3], unsigned short s[16])
{
    //
    // Unpack a 3-byte block into 4 by 4 identical 16-bit pixels.
    //

    #if defined (DEBUG)
	assert (b[2] == 0xfc);
    #endif

    s[0] = (b[0] << 8) | b[1];

    if (s[0] & 0x8000)
	s[0] &= 0x7fff;
    else
	s[0] = ~s[0];

    for (int i = 1; i < 16; ++i)
	s[i] = s[0];
}


void
notEnoughData ()
{
    throw Iex::InputExc ("Error decompressing data "
			 "(input data are shorter than expected).");
}


void
tooMuchData ()
{
    throw Iex::InputExc ("Error decompressing data "
			 "(input data are longer than expected).");
}

} // namespace


struct B44Compressor::ChannelData
{
    unsigned short *	start;
    unsigned short *	end;
    int			nx;
    int			ny;
    int			ys;
    PixelType		type;
    bool		pLinear;
    int			size;
};


B44Compressor::B44Compressor
    (const Header &hdr,
     int maxScanLineSize,
     int numScanLines,
     bool optFlatFields)
:
    Compressor (hdr),
    _maxScanLineSize (maxScanLineSize),
    _optFlatFields (optFlatFields),
    _format (XDR),
    _numScanLines (numScanLines),
    _tmpBuffer (0),
    _outBuffer (0),
    _numChans (0),
    _channels (hdr.channels()),
    _channelData (0)
{
    //
    // Allocate buffers for compressed an uncompressed pixel data,
    // allocate a set of ChannelData structs to help speed up the
    // compress() and uncompress() functions, below, and determine
    // if uncompressed pixel data should be in native or Xdr format.
    //

    _tmpBuffer = new unsigned short [maxScanLineSize * numScanLines];

    const ChannelList &channels = header().channels();
    int numHalfChans = 0;

    for (ChannelList::ConstIterator c = channels.begin();
	 c != channels.end();
	 ++c)
    {
	assert (pixelTypeSize (c.channel().type) % pixelTypeSize (HALF) == 0);
	++_numChans;

	if (c.channel().type == HALF)
	    ++numHalfChans;
    }

    //
    // Compressed data may be larger than the input data
    //

    int padding = 12 * numHalfChans * (numScanLines + 3) / 4;

    _outBuffer = new char [maxScanLineSize * numScanLines + padding];
    _channelData = new ChannelData[_numChans];

    int i = 0;

    for (ChannelList::ConstIterator c = channels.begin();
	 c != channels.end();
	 ++c, ++i)
    {
	_channelData[i].ys = c.channel().ySampling;
	_channelData[i].type = c.channel().type;
	_channelData[i].pLinear = c.channel().pLinear;
	_channelData[i].size =
	    pixelTypeSize (c.channel().type) / pixelTypeSize (HALF);
    }

    const Box2i &dataWindow = hdr.dataWindow();

    _minX = dataWindow.min.x;
    _maxX = dataWindow.max.x;
    _maxY = dataWindow.max.y;