📄 imfb44compressor.cpp
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///////////////////////////////////////////////////////////////////////////
//
// 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;
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