/src/dng_sdk/source/dng_lossless_jpeg.cpp

Source
/*****************************************************************************/
// Copyright 2006-2007 Adobe Systems Incorporated
// All Rights Reserved.
//
// NOTICE:  Adobe permits you to use, modify, and distribute this file in
// accordance with the terms of the Adobe license agreement accompanying it.
/*****************************************************************************/

/* $Id: //mondo/dng_sdk_1_4/dng_sdk/source/dng_lossless_jpeg.cpp#2 $ */ 
/* $DateTime: 2012/06/01 07:28:57 $ */
/* $Change: 832715 $ */
/* $Author: tknoll $ */
 
/*****************************************************************************/

// Lossless JPEG code adapted from:

/* Copyright (C) 1991, 1992, Thomas G. Lane.
 * Part of the Independent JPEG Group's software.
 * See the file Copyright for more details.
 *
 * Copyright (c) 1993 Brian C. Smith, The Regents of the University
 * of California
 * All rights reserved.
 * 
 * Copyright (c) 1994 Kongji Huang and Brian C. Smith.
 * Cornell University
 * All rights reserved.
 * 
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 * 
 * IN NO EVENT SHALL CORNELL UNIVERSITY BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF CORNELL
 * UNIVERSITY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * CORNELL UNIVERSITY SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND CORNELL UNIVERSITY HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 */
 
/*****************************************************************************/

#include "dng_lossless_jpeg.h"

#include "dng_assertions.h"
#include "dng_exceptions.h"
#include "dng_memory.h"
#include "dng_stream.h"
#include "dng_tag_codes.h"

/*****************************************************************************/

// This module contains routines that should be as fast as possible, even
// at the expense of slight code size increases.

#include "dng_fast_module.h"

/*****************************************************************************/

// The qSupportCanon_sRAW stuff not actually required for DNG support, but
// only included to allow this code to be used on Canon sRAW files.

#ifndef qSupportCanon_sRAW
#define qSupportCanon_sRAW 1
#endif

// The qSupportHasselblad_3FR stuff not actually required for DNG support, but
// only included to allow this code to be used on Hasselblad 3FR files.

#ifndef qSupportHasselblad_3FR
#define qSupportHasselblad_3FR 1
#endif

/*****************************************************************************/

/*
 * One of the following structures is created for each huffman coding
 * table.  We use the same structure for encoding and decoding, so there
 * may be some extra fields for encoding that aren't used in the decoding
 * and vice-versa.
 */
 
struct HuffmanTable
  {
  
    /*
     * These two fields directly represent the contents of a JPEG DHT
     * marker
     */
    uint8 bits[17];
    uint8 huffval[256];

    /*
     * The remaining fields are computed from the above to allow more
     * efficient coding and decoding.  These fields should be considered
     * private to the Huffman compression & decompression modules.
     */

    uint16 mincode[17];
    int32 maxcode[18];
    int16 valptr[17];
    int32 numbits[256];
    int32 value[256];
    
    uint16 ehufco[256];
    int8 ehufsi[256];
    
  };

/*****************************************************************************/

// Computes the derived fields in the Huffman table structure.
 
static void FixHuffTbl (HuffmanTable *htbl)
  {
  
  int32 l;
  int32 i;
  
  const uint32 bitMask [] =
    {
    0xffffffff, 0x7fffffff, 0x3fffffff, 0x1fffffff,
        0x0fffffff, 0x07ffffff, 0x03ffffff, 0x01ffffff,
        0x00ffffff, 0x007fffff, 0x003fffff, 0x001fffff,
        0x000fffff, 0x0007ffff, 0x0003ffff, 0x0001ffff,
        0x0000ffff, 0x00007fff, 0x00003fff, 0x00001fff,
        0x00000fff, 0x000007ff, 0x000003ff, 0x000001ff,
        0x000000ff, 0x0000007f, 0x0000003f, 0x0000001f,
        0x0000000f, 0x00000007, 0x00000003, 0x00000001
        };
        
    // Figure C.1: make table of Huffman code length for each symbol
    // Note that this is in code-length order.

  int8 huffsize [257];
  
    int32 p = 0;
    
  for (l = 1; l <= 16; l++)
      {
      
        for (i = 1; i <= (int32) htbl->bits [l]; i++)
            huffsize [p++] = (int8) l;

      }
      
    huffsize [p] = 0;
    
    int32 lastp = p;

  // Figure C.2: generate the codes themselves
  // Note that this is in code-length order.

  uint16 huffcode [257];
  
  uint16 code = 0;
    
    int32 si = huffsize [0];
    
    p = 0;
    
    while (huffsize [p])
      {
      
        while (((int32) huffsize [p]) == si) 
          {
            huffcode [p++] = code;
            code++;
          }
          
        code <<= 1;
        
        si++;
        
      }

    // Figure C.3: generate encoding tables
    // These are code and size indexed by symbol value
    // Set any codeless symbols to have code length 0; this allows
    // EmitBits to detect any attempt to emit such symbols.

    memset (htbl->ehufsi, 0, sizeof (htbl->ehufsi));

    for (p = 0; p < lastp; p++)
      {
      
        htbl->ehufco [htbl->huffval [p]] = huffcode [p];
        htbl->ehufsi [htbl->huffval [p]] = huffsize [p];
        
      }
    
  // Figure F.15: generate decoding tables
 
  p = 0;
  
    for (l = 1; l <= 16; l++)
      {
      
        if (htbl->bits [l])
          {
          
            htbl->valptr  [l] = (int16) p;
            htbl->mincode [l] = huffcode [p];
            
            p += htbl->bits [l];
            
            htbl->maxcode [l] = huffcode [p - 1];
            
          }
          
        else 
          {
            htbl->maxcode [l] = -1;
          }

      }

    // We put in this value to ensure HuffDecode terminates.

    htbl->maxcode[17] = 0xFFFFFL;

    // Build the numbits, value lookup tables.
    // These table allow us to gather 8 bits from the bits stream,
    // and immediately lookup the size and value of the huffman codes.
    // If size is zero, it means that more than 8 bits are in the huffman
    // code (this happens about 3-4% of the time).

    memset (htbl->numbits, 0, sizeof (htbl->numbits));
    
  for (p = 0; p < lastp; p++)
    {
    
        int32 size = huffsize [p];
        
        if (size <= 8)
          {
          
            int32 value = htbl->huffval [p];
            
            code = huffcode [p];
            
            int32 ll = code << (8  -size);
            
        int32 ul = (size < 8 ? ll | bitMask [24 + size]
                     : ll);
            if (ul >= static_cast<int32>(sizeof(htbl->numbits) / sizeof(htbl->numbits[0])) ||
                ul >= static_cast<int32>(sizeof(htbl->value) / sizeof(htbl->value[0])))
                {
                ThrowBadFormat ();
                }
  
            for (i = ll; i <= ul; i++)
              {
                htbl->numbits [i] = size;
                htbl->value   [i] = value;
              }
              
      }

    }

  }

/*****************************************************************************/

/*
 * The following structure stores basic information about one component.
 */
 
struct JpegComponentInfo
  {
  
    /*
     * These values are fixed over the whole image.
     * They are read from the SOF marker.
     */
    int16 componentId;    /* identifier for this component (0..255) */
    int16 componentIndex; /* its index in SOF or cPtr->compInfo[]   */

    /*
     * Downsampling is not normally used in lossless JPEG, although
     * it is permitted by the JPEG standard (DIS). We set all sampling 
     * factors to 1 in this program.
     */
    int16 hSampFactor;    /* horizontal sampling factor */
    int16 vSampFactor;    /* vertical sampling factor   */

    /*
     * Huffman table selector (0..3). The value may vary
     * between scans. It is read from the SOS marker.
     */
    int16 dcTblNo;

  };

/*
 * One of the following structures is used to pass around the
 * decompression information.
 */
 
struct DecompressInfo
  {
  
    /*
     * Image width, height, and image data precision (bits/sample)
     * These fields are set by ReadFileHeader or ReadScanHeader
     */ 
    int32 imageWidth;
    int32 imageHeight;
    int32 dataPrecision;

    /*
     * compInfo[i] describes component that appears i'th in SOF
     * numComponents is the # of color components in JPEG image.
     */
    JpegComponentInfo *compInfo;
    int16 numComponents;

    /*
     * *curCompInfo[i] describes component that appears i'th in SOS.
     * compsInScan is the # of color components in current scan.
     */
    JpegComponentInfo *curCompInfo[4];
    int16 compsInScan;

    /*
     * MCUmembership[i] indexes the i'th component of MCU into the
     * curCompInfo array.
     */
    int16 MCUmembership[10];

    /*
     * ptrs to Huffman coding tables, or NULL if not defined
     */
    HuffmanTable *dcHuffTblPtrs[4];

    /* 
     * prediction selection value (PSV) and point transform parameter (Pt)
     */
    int32 Ss;
    int32 Pt;

    /*
     * In lossless JPEG, restart interval shall be an integer
     * multiple of the number of MCU in a MCU row.
     */
    int32 restartInterval;/* MCUs per restart interval, 0 = no restart */
    int32 restartInRows; /*if > 0, MCU rows per restart interval; 0 = no restart*/

    /*
     * these fields are private data for the entropy decoder
     */
    int32 restartRowsToGo;  /* MCUs rows left in this restart interval */
    int16 nextRestartNum; /* # of next RSTn marker (0..7) */
    
  };

/*****************************************************************************/

// An MCU (minimum coding unit) is an array of samples.

typedef uint16 ComponentType;     // the type of image components

typedef ComponentType *MCU;     // MCU - array of samples

/*****************************************************************************/

class dng_lossless_decoder
  {
  
  private:
  
    dng_stream *fStream;    // Input data.
    
    dng_spooler *fSpooler;    // Output data.
        
    bool fBug16;        // Decode data with the "16-bit" bug.

    dng_memory_data huffmanBuffer [4];
    
    dng_memory_data compInfoBuffer;
    
    DecompressInfo info;
    
    dng_memory_data mcuBuffer1;
    dng_memory_data mcuBuffer2;
    dng_memory_data mcuBuffer3;
    dng_memory_data mcuBuffer4;
  
    MCU *mcuROW1;
    MCU *mcuROW2;
    
    uint64 getBuffer;     // current bit-extraction buffer
    int32 bitsLeft;       // # of unused bits in it
        
    #if qSupportHasselblad_3FR
    bool fHasselblad3FR;
    #endif

  public:
  
    dng_lossless_decoder (dng_stream *stream,
                  dng_spooler *spooler,
                  bool bug16);
  
    void StartRead (uint32 &imageWidth,
            uint32 &imageHeight,
            uint32 &imageChannels);

    void FinishRead ();

  private:

    uint8 GetJpegChar ()
      {
      return fStream->Get_uint8 ();
      }
      
    void UnGetJpegChar ()
      {
      fStream->SetReadPosition (fStream->Position () - 1);
      }
      
    uint16 Get2bytes ();
  
    void SkipVariable ();

    void GetDht ();

    void GetDri ();

    void GetApp0 ();

    void GetSof (int32 code);

    void GetSos ();

    void GetSoi ();
    
    int32 NextMarker ();

    JpegMarker ProcessTables ();
    
    void ReadFileHeader ();

    int32 ReadScanHeader ();

    void DecoderStructInit ();

    void HuffDecoderInit ();

    void ProcessRestart ();

    int32 QuickPredict (int32 col,
                int32 curComp,
                MCU *curRowBuf,
                MCU *prevRowBuf);

    void FillBitBuffer (int32 nbits);

    int32 show_bits8 ();

    void flush_bits (int32 nbits);

    int32 get_bits (int32 nbits);

    int32 get_bit ();

    int32 HuffDecode (HuffmanTable *htbl);

    void HuffExtend (int32 &x, int32 s);

    void PmPutRow (MCU *buf,
             int32 numComp,
             int32 numCol,
             int32 row);

    void DecodeFirstRow (MCU *curRowBuf);

    void DecodeImage ();
    
    // Hidden copy constructor and assignment operator.
    
    dng_lossless_decoder (const dng_lossless_decoder &decoder);
    
    dng_lossless_decoder & operator= (const dng_lossless_decoder &decoder);
    
  };

/*****************************************************************************/

dng_lossless_decoder::dng_lossless_decoder (dng_stream *stream,
                          dng_spooler *spooler,
                          bool bug16)
                  
  : fStream  (stream )
  , fSpooler (spooler)
  , fBug16   (bug16  )
  
  , compInfoBuffer ()
  , info           ()
  , mcuBuffer1     ()
  , mcuBuffer2     ()
  , mcuBuffer3     ()
  , mcuBuffer4     ()
  , mcuROW1      (NULL)
  , mcuROW2      (NULL)
  , getBuffer      (0)
  , bitsLeft     (0)
  
  #if qSupportHasselblad_3FR
  , fHasselblad3FR (false)
  #endif
  
  {
  
  memset (&info, 0, sizeof (info));
  
  }

/*****************************************************************************/

uint16 dng_lossless_decoder::Get2bytes ()
  {
  
    uint16 a = GetJpegChar ();
    
    return (uint16) ((a << 8) + GetJpegChar ());
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * SkipVariable --
 *
 *  Skip over an unknown or uninteresting variable-length marker
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  Bitstream is parsed over marker.
 *
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_decoder::SkipVariable ()
  {
  
    uint32 length = Get2bytes () - 2;
    
    fStream->Skip (length);

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GetDht --
 *
 *  Process a DHT marker
 *
 * Results:
 *  None
 *
 * Side effects:
 *  A huffman table is read.
 *  Exits on error.
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_decoder::GetDht ()
  {
  
    int32 length = Get2bytes () - 2;
    
    while (length > 0)
      {

    int32 index = GetJpegChar ();
      
    if (index < 0 || index >= 4)
      {
        ThrowBadFormat ();
      }

    HuffmanTable *&htblptr = info.dcHuffTblPtrs [index];

    if (htblptr == NULL)
      {
      
      huffmanBuffer [index] . Allocate (sizeof (HuffmanTable));
      
        htblptr = (HuffmanTable *) huffmanBuffer [index] . Buffer ();
        
      }

    htblptr->bits [0] = 0;
    
      int32 count = 0;
      
    for (int32 i = 1; i <= 16; i++)
      {
      
        htblptr->bits [i] = GetJpegChar ();
        
        count += htblptr->bits [i];
        
      }

    if (count > 256) 
      {
        ThrowBadFormat ();
      }

    for (int32 j = 0; j < count; j++)
      {
      
        htblptr->huffval [j] = GetJpegChar ();
        
        }

    length -= 1 + 16 + count;

      }
      
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GetDri --
 *
 *  Process a DRI marker
 *
 * Results:
 *  None
 *
 * Side effects:
 *  Exits on error.
 *  Bitstream is parsed.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::GetDri ()
  {
  
    if (Get2bytes () != 4)
      {
    ThrowBadFormat ();
    }
    
    info.restartInterval = Get2bytes ();

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GetApp0 --
 *
 *  Process an APP0 marker.
 *
 * Results:
 *  None
 *
 * Side effects:
 *  Bitstream is parsed
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::GetApp0 ()
  {

  SkipVariable ();
  
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GetSof --
 *
 *  Process a SOFn marker
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  Bitstream is parsed
 *  Exits on error
 *  info structure is filled in
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_decoder::GetSof (int32 /*code*/)
  {
  
    int32 length = Get2bytes ();

    info.dataPrecision = GetJpegChar ();
    info.imageHeight   = Get2bytes   ();
    info.imageWidth    = Get2bytes   ();
    info.numComponents = GetJpegChar ();

    // We don't support files in which the image height is initially
    // specified as 0 and is later redefined by DNL.  As long as we
    // have to check that, might as well have a general sanity check.
     
    if ((info.imageHeight   <= 0) ||
    (info.imageWidth    <= 0) || 
    (info.numComponents <= 0))
    {
    ThrowBadFormat ();
      }

  // Lossless JPEG specifies data precision to be from 2 to 16 bits/sample.

  const int32 MinPrecisionBits = 2;
  const int32 MaxPrecisionBits = 16;

    if ((info.dataPrecision < MinPrecisionBits) ||
        (info.dataPrecision > MaxPrecisionBits))
        {
    ThrowBadFormat ();
      }
      
    // Check length of tag.

    if (length != (info.numComponents * 3 + 8))
      {
    ThrowBadFormat ();
      }
      
    // Allocate per component info.
    
    // We can cast info.numComponents to a uint32 because the check above
    // guarantees that it cannot be negative.
    compInfoBuffer.Allocate (static_cast<uint32> (info.numComponents),
                             sizeof (JpegComponentInfo));
    
    info.compInfo = (JpegComponentInfo *) compInfoBuffer.Buffer ();
                   
    // Read in the per compent info.

    for (int32 ci = 0; ci < info.numComponents; ci++)
      {
      
      JpegComponentInfo *compptr = &info.compInfo [ci];
      
    compptr->componentIndex = (int16) ci;
    
    compptr->componentId = GetJpegChar ();
    
      int32 c = GetJpegChar ();
      
    compptr->hSampFactor = (int16) ((c >> 4) & 15);
    compptr->vSampFactor = (int16) ((c     ) & 15);
    
        (void) GetJpegChar ();   /* skip Tq */
        
      }

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GetSos --
 *
 *  Process a SOS marker
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  Bitstream is parsed.
 *  Exits on error.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::GetSos ()
  {
  
    int32 length = Get2bytes ();

    // Get the number of image components.

    int32 n = GetJpegChar ();
    info.compsInScan = (int16) n;
    
    // Check length.
    
    length -= 3;

    if (length != (n * 2 + 3) || n < 1 || n > 4)
      {
    ThrowBadFormat ();
    }
  
  // Find index and huffman table for each component.

    for (int32 i = 0; i < n; i++)
      {
      
    int32 cc = GetJpegChar ();
    int32 c  = GetJpegChar ();
    
    int32 ci;
    
    for (ci = 0; ci < info.numComponents; ci++)
      {
      
        if (cc == info.compInfo[ci].componentId)
          {
        break;
          }
          
        }

    if (ci >= info.numComponents) 
      {
        ThrowBadFormat ();
      }

      JpegComponentInfo *compptr = &info.compInfo [ci];
      
    info.curCompInfo [i] = compptr;
    
    compptr->dcTblNo = (int16) ((c >> 4) & 15);
    
      }

    // Get the PSV, skip Se, and get the point transform parameter.

    info.Ss = GetJpegChar (); 
    
    (void) GetJpegChar ();
    
    info.Pt = GetJpegChar () & 0x0F;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GetSoi --
 *
 *  Process an SOI marker
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  Bitstream is parsed.
 *  Exits on error.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::GetSoi ()
  {

    // Reset all parameters that are defined to be reset by SOI
     
    info.restartInterval = 0;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * NextMarker --
 *
 *      Find the next JPEG marker Note that the output might not
 *  be a valid marker code but it will never be 0 or FF
 *
 * Results:
 *  The marker found.
 *
 * Side effects:
 *  Bitstream is parsed.
 *
 *--------------------------------------------------------------
 */

int32 dng_lossless_decoder::NextMarker ()
  {
  
    int32 c;

    do
      {

    // skip any non-FF bytes
    
    do 
      {
        c = GetJpegChar ();
      }
    while (c != 0xFF);
    
    // skip any duplicate FFs, since extra FFs are legal
    
    do 
      {
      c = GetJpegChar();
      } 
    while (c == 0xFF);
    
    }
  while (c == 0);    // repeat if it was a stuffed FF/00

    return c;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * ProcessTables --
 *
 *  Scan and process JPEG markers that can appear in any order
 *  Return when an SOI, EOI, SOFn, or SOS is found
 *
 * Results:
 *  The marker found.
 *
 * Side effects:
 *  Bitstream is parsed.
 *
 *--------------------------------------------------------------
 */

JpegMarker dng_lossless_decoder::ProcessTables ()
  {
  
    while (true)
      {
    
    int32 c = NextMarker ();
  
    switch (c)
      {
      
      case M_SOF0:
      case M_SOF1:
      case M_SOF2:
      case M_SOF3:
      case M_SOF5:
      case M_SOF6:
      case M_SOF7:
      case M_JPG:
      case M_SOF9:
      case M_SOF10:
      case M_SOF11:
      case M_SOF13:
      case M_SOF14:
      case M_SOF15:
      case M_SOI:
      case M_EOI:
      case M_SOS:
          return (JpegMarker) c;

      case M_DHT:
          GetDht ();
          break;

      case M_DQT:
          break;

      case M_DRI:
          GetDri ();
          break;

      case M_APP0:
          GetApp0 ();
          break;

      case M_RST0:  // these are all parameterless
      case M_RST1:
      case M_RST2:
      case M_RST3:
      case M_RST4:
      case M_RST5:
      case M_RST6:
      case M_RST7:
      case M_TEM:
          break;

      default:    // must be DNL, DHP, EXP, APPn, JPGn, COM, or RESn
          SkipVariable ();
          break;
          
      }
      
      }

      return M_ERROR;
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * ReadFileHeader --
 *
 *  Initialize and read the stream header (everything through
 *  the SOF marker).
 *
 * Results:
 *  None
 *
 * Side effects:
 *  Exit on error.
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_decoder::ReadFileHeader ()
  {
  
    // Demand an SOI marker at the start of the stream --- otherwise it's
    // probably not a JPEG stream at all.

    int32 c  = GetJpegChar ();
    int32 c2 = GetJpegChar ();
    
    if ((c != 0xFF) || (c2 != M_SOI)) 
      {
    ThrowBadFormat ();
      }
      
    // OK, process SOI

    GetSoi ();

    // Process markers until SOF

    c = ProcessTables ();

    switch (c)
      {
      
    case M_SOF0:
    case M_SOF1:
    case M_SOF3:
      GetSof (c);
      break;

      default:
      ThrowBadFormat ();
      break;
      
      }

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * ReadScanHeader --
 *
 *  Read the start of a scan (everything through the SOS marker).
 *
 * Results:
 *  1 if find SOS, 0 if find EOI
 *
 * Side effects:
 *  Bitstream is parsed, may exit on errors.
 *
 *--------------------------------------------------------------
 */

int32 dng_lossless_decoder::ReadScanHeader ()
  {

    // Process markers until SOS or EOI

    int32 c = ProcessTables ();

    switch (c)
      {
      
    case M_SOS:
      GetSos ();
      return 1;

      case M_EOI:
      return 0;

      default:
      ThrowBadFormat ();
      break;
      
      }
      
    return 0;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * DecoderStructInit --
 *
 *  Initalize the rest of the fields in the decompression
 *  structure.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::DecoderStructInit ()
  {
  
  int32 ci;
  
  #if qSupportCanon_sRAW
  
  bool canon_sRAW = (info.numComponents == 3) &&
            (info.compInfo [0].hSampFactor == 2) &&
            (info.compInfo [1].hSampFactor == 1) &&
            (info.compInfo [2].hSampFactor == 1) &&
            (info.compInfo [0].vSampFactor == 1) &&
            (info.compInfo [1].vSampFactor == 1) &&
            (info.compInfo [2].vSampFactor == 1) &&
            (info.dataPrecision == 15) &&
            (info.Ss == 1) &&
            ((info.imageWidth & 1) == 0);
            
  bool canon_sRAW2 = (info.numComponents == 3) &&
             (info.compInfo [0].hSampFactor == 2) &&
             (info.compInfo [1].hSampFactor == 1) &&
             (info.compInfo [2].hSampFactor == 1) &&
             (info.compInfo [0].vSampFactor == 2) &&
             (info.compInfo [1].vSampFactor == 1) &&
             (info.compInfo [2].vSampFactor == 1) &&
             (info.dataPrecision == 15) &&
             (info.Ss == 1) &&
             ((info.imageWidth  & 1) == 0) &&
             ((info.imageHeight & 1) == 0);
             
  if (!canon_sRAW && !canon_sRAW2)
  
  #endif
  
    {
  
    // Check sampling factor validity.

    for (ci = 0; ci < info.numComponents; ci++)
      {
      
      JpegComponentInfo *compPtr = &info.compInfo [ci];
      
      if (compPtr->hSampFactor != 1 ||
        compPtr->vSampFactor != 1) 
        {
        ThrowBadFormat ();
        }
    
      }
      
    }
  
    // Prepare array describing MCU composition.

  if (info.compsInScan < 0 || info.compsInScan > 4)
    {
      ThrowBadFormat ();
    }

  for (ci = 0; ci < info.compsInScan; ci++)
    {
        info.MCUmembership [ci] = (int16) ci;
    }

  // Initialize mucROW1 and mcuROW2 which buffer two rows of
    // pixels for predictor calculation.
    
  // This multiplication cannot overflow because info.compsInScan is
  // guaranteed to be between 0 and 4 inclusive (see checks above).
  int32 mcuSize = info.compsInScan * (uint32) sizeof (ComponentType);
  
  mcuBuffer1.Allocate (info.imageWidth, sizeof (MCU));
  mcuBuffer2.Allocate (info.imageWidth, sizeof (MCU));
  
  mcuROW1 = (MCU *) mcuBuffer1.Buffer ();
  mcuROW2 = (MCU *) mcuBuffer2.Buffer ();
  
  mcuBuffer3.Allocate (info.imageWidth, mcuSize);
  mcuBuffer4.Allocate (info.imageWidth, mcuSize);
  
  mcuROW1 [0] = (ComponentType *) mcuBuffer3.Buffer ();
  mcuROW2 [0] = (ComponentType *) mcuBuffer4.Buffer ();
  
  for (int32 j = 1; j < info.imageWidth; j++)
    {
    
    mcuROW1 [j] = mcuROW1 [j - 1] + info.compsInScan;
    mcuROW2 [j] = mcuROW2 [j - 1] + info.compsInScan;
  
    }
  
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * HuffDecoderInit --
 *
 *  Initialize for a Huffman-compressed scan.
 *  This is invoked after reading the SOS marker.
 *
 * Results:
 *  None
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::HuffDecoderInit ()
  {
  
    // Initialize bit parser state
 
  getBuffer = 0;
    bitsLeft  = 0;
    
    // Prepare Huffman tables.

    for (int16 ci = 0; ci < info.compsInScan; ci++)
      {
      
    JpegComponentInfo *compptr = info.curCompInfo [ci];
    
    // Make sure requested tables are present
    
    if (compptr->dcTblNo < 0 || compptr->dcTblNo > 3)
      {
      ThrowBadFormat ();
      }

    if (info.dcHuffTblPtrs [compptr->dcTblNo] == NULL) 
      { 
        ThrowBadFormat ();
      }

    // Compute derived values for Huffman tables.
    // We may do this more than once for same table, but it's not a
    // big deal

    FixHuffTbl (info.dcHuffTblPtrs [compptr->dcTblNo]);

      }

    // Initialize restart stuff

  info.restartInRows   = info.restartInterval / info.imageWidth;
    info.restartRowsToGo = info.restartInRows;
    info.nextRestartNum  = 0;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * ProcessRestart --
 *
 *  Check for a restart marker & resynchronize decoder.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  BitStream is parsed, bit buffer is reset, etc.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_decoder::ProcessRestart ()
  {
  
  // Throw away and unused odd bits in the bit buffer.
  
  fStream->SetReadPosition (fStream->Position () - bitsLeft / 8);
  
  bitsLeft  = 0;
  getBuffer = 0;
  
    // Scan for next JPEG marker

    int32 c;

    do
      {
      
    // skip any non-FF bytes
    
    do 
      { 
        c = GetJpegChar ();
      }
    while (c != 0xFF);
    
    // skip any duplicate FFs
    
    do
      {
      c = GetJpegChar ();
      }
    while (c == 0xFF);
    
      }
    while (c == 0);    // repeat if it was a stuffed FF/00
    
    // Verify correct restart code.

    if (c != (M_RST0 + info.nextRestartNum))
      {
    ThrowBadFormat ();
      }

    // Update restart state.

    info.restartRowsToGo = info.restartInRows;
    info.nextRestartNum  = (info.nextRestartNum + 1) & 7;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * QuickPredict --
 *
 *      Calculate the predictor for sample curRowBuf[col][curComp].
 *  It does not handle the special cases at image edges, such 
 *      as first row and first column of a scan. We put the special 
 *  case checkings outside so that the computations in main
 *  loop can be simpler. This has enhenced the performance
 *  significantly.
 *
 * Results:
 *      predictor is passed out.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */
 
inline int32 dng_lossless_decoder::QuickPredict (int32 col,
                             int32 curComp,
                             MCU *curRowBuf,
                             MCU *prevRowBuf)
  {
  
    int32 diag  = prevRowBuf [col - 1] [curComp];
    int32 upper = prevRowBuf [col    ] [curComp];
    int32 left  = curRowBuf  [col - 1] [curComp];

    switch (info.Ss)
      {
      
    case 0:
      return 0;
      
    case 1:
      return left;

    case 2:
      return upper;

    case 3:
      return diag;

    case 4:
      return left + upper - diag;

    case 5:
      return left + ((upper - diag) >> 1);

    case 6:
          return upper + ((left - diag) >> 1);

    case 7:
            return (left + upper) >> 1;

    default:
      {
      ThrowBadFormat ();
            return 0;
            }
              
      }
     
  }
  
/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * FillBitBuffer --
 *
 *  Load up the bit buffer with at least nbits
 *  Process any stuffed bytes at this time.
 *
 * Results:
 *  None
 *
 * Side effects:
 *  The bitwise global variables are updated.
 *
 *--------------------------------------------------------------
 */

inline void dng_lossless_decoder::FillBitBuffer (int32 nbits)
  {
  
  const int32 kMinGetBits = sizeof (uint32) * 8 - 7;
  
  #if qSupportHasselblad_3FR
  
  if (fHasselblad3FR)
    {
    
    while (bitsLeft < kMinGetBits)
      {
      
      int32 c0 = GetJpegChar ();
      int32 c1 = GetJpegChar ();
      int32 c2 = GetJpegChar ();
      int32 c3 = GetJpegChar ();
      
      getBuffer = (getBuffer << 8) | c3;
      getBuffer = (getBuffer << 8) | c2;
      getBuffer = (getBuffer << 8) | c1;
      getBuffer = (getBuffer << 8) | c0;
      
      bitsLeft += 32;
      
      }
      
    return;
    
    }
  
  #endif
  
    while (bitsLeft < kMinGetBits)
      {
      
    int32 c = GetJpegChar ();

    // If it's 0xFF, check and discard stuffed zero byte

    if (c == 0xFF)
      {
      
      int32 c2 = GetJpegChar ();
      
        if (c2 != 0)
          {

        // Oops, it's actually a marker indicating end of
        // compressed data.  Better put it back for use later.

        UnGetJpegChar ();
        UnGetJpegChar ();

        // There should be enough bits still left in the data
        // segment; if so, just break out of the while loop.

        if (bitsLeft >= nbits)
            break;

        // Uh-oh.  Corrupted data: stuff zeroes into the data
        // stream, since this sometimes occurs when we are on the
        // last show_bits8 during decoding of the Huffman
        // segment.

        c = 0;
        
          }
          
      }
      
    getBuffer = (getBuffer << 8) | c;
    
    bitsLeft += 8;
    
      }
 
  }

/*****************************************************************************/

inline int32 dng_lossless_decoder::show_bits8 ()
  {
  
  if (bitsLeft < 8)
    FillBitBuffer (8);
    
  return (int32) ((getBuffer >> (bitsLeft - 8)) & 0xff);
  
  }

/*****************************************************************************/

inline void dng_lossless_decoder::flush_bits (int32 nbits)
  {
  
  bitsLeft -= nbits;
  
  }

/*****************************************************************************/

inline int32 dng_lossless_decoder::get_bits (int32 nbits)
  {
  
  if (nbits > 16)
    {
    ThrowBadFormat ();
    }
  
  if (bitsLeft < nbits)
    FillBitBuffer (nbits);
    
  return (int32) ((getBuffer >> (bitsLeft -= nbits)) & (0x0FFFF >> (16 - nbits)));
  
  }

/*****************************************************************************/

inline int32 dng_lossless_decoder::get_bit ()
  {
  
  if (!bitsLeft)
    FillBitBuffer (1);
    
  return (int32) ((getBuffer >> (--bitsLeft)) & 1);
  
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * HuffDecode --
 *
 *  Taken from Figure F.16: extract next coded symbol from
 *  input stream.  This should becode a macro.
 *
 * Results:
 *  Next coded symbol
 *
 * Side effects:
 *  Bitstream is parsed.
 *
 *--------------------------------------------------------------
 */
 
inline int32 dng_lossless_decoder::HuffDecode (HuffmanTable *htbl)
  {
  
  if (htbl == nullptr) {
    ThrowBadFormat ();
  }

    // If the huffman code is less than 8 bits, we can use the fast
    // table lookup to get its value.  It's more than 8 bits about
    // 3-4% of the time.

    int32 code = show_bits8 ();
    
    if (htbl->numbits [code])
      {
      
    flush_bits (htbl->numbits [code]);
    
    return htbl->value [code];
    
      }
      
    else
      {
      
    flush_bits (8);
    
    int32 l = 8;
    
    while (code > htbl->maxcode [l]) 
      {
        code = (code << 1) | get_bit ();
        l++;
      }

    // With garbage input we may reach the sentinel value l = 17.

    if (l > 16) 
      {
        return 0;   // fake a zero as the safest result
      }
    else
      {
        return htbl->huffval [htbl->valptr [l] +
                    ((int32) (code - htbl->mincode [l]))];
      }
      
      }
      
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * HuffExtend --
 *
 *  Code and table for Figure F.12: extend sign bit
 *
 * Results:
 *  The extended value.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

inline void dng_lossless_decoder::HuffExtend (int32 &x, int32 s)
  {

  if (x < (0x08000 >> (16 - s)))
    {
    x += -(1 << s) + 1;
    }

  }

/*****************************************************************************/

// Called from DecodeImage () to write one row.
 
void dng_lossless_decoder::PmPutRow (MCU *buf,
                     int32 numComp,
                     int32 numCol,
                     int32 /* row */)
  {
  
  uint16 *sPtr = &buf [0] [0];
  
  uint32 pixels = numCol * numComp;
  
  fSpooler->Spool (sPtr, pixels * (uint32) sizeof (uint16));
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * DecodeFirstRow --
 *
 *  Decode the first raster line of samples at the start of 
 *      the scan and at the beginning of each restart interval.
 *  This includes modifying the component value so the real
 *      value, not the difference is returned.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  Bitstream is parsed.
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_decoder::DecodeFirstRow (MCU *curRowBuf)
  {
  
    int32 compsInScan = info.compsInScan;
    
    // Process the first column in the row.

    for (int32 curComp = 0; curComp < compsInScan; curComp++) 
      {
      
        int32 ci = info.MCUmembership [curComp];
        
        JpegComponentInfo *compptr = info.curCompInfo [ci];
        
        HuffmanTable *dctbl = info.dcHuffTblPtrs [compptr->dcTblNo];

        // Section F.2.2.1: decode the difference

      int32 d = 0;
  
        int32 s = HuffDecode (dctbl);
        
        if (s)
          {
          
          if (s == 16 && !fBug16)
            {
            d = -32768;
            }
          
          else
            {
        d = get_bits (s);
              HuffExtend (d, s);
              }

            }

    // Add the predictor to the difference.

      int32 Pr = info.dataPrecision;
      int32 Pt = info.Pt;
    
        curRowBuf [0] [curComp] = (ComponentType) (d + (1 << (Pr-Pt-1)));
        
      }
      
    // Process the rest of the row.
    
    int32 numCOL = info.imageWidth;
    
    for (int32 col = 1; col < numCOL; col++)
      {

        for (int32 curComp = 0; curComp < compsInScan; curComp++)
          {
          
            int32 ci = info.MCUmembership [curComp];
            
            JpegComponentInfo *compptr = info.curCompInfo [ci];
            
            HuffmanTable *dctbl = info.dcHuffTblPtrs [compptr->dcTblNo];

      // Section F.2.2.1: decode the difference

        int32 d = 0;
    
          int32 s = HuffDecode (dctbl);
          
          if (s)
            {

            if (s == 16 && !fBug16)
              {
              d = -32768;
              }
            
            else
              {
          d = get_bits (s);
                HuffExtend (d, s);
                }

              }
              
      // Add the predictor to the difference.

            curRowBuf [col] [curComp] = (ComponentType) (d + curRowBuf [col-1] [curComp]);
            
          }
          
      }
      
    // Update the restart counter

    if (info.restartInRows)
      {
        info.restartRowsToGo--;
      }
      
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * DecodeImage --
 *
 *      Decode the input stream. This includes modifying
 *      the component value so the real value, not the
 *      difference is returned.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Bitstream is parsed.
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_decoder::DecodeImage ()
  {
  
  #define swap(type,a,b) {type c; c=(a); (a)=(b); (b)=c;}

    int32 numCOL      = info.imageWidth;
    int32 numROW    = info.imageHeight;
    int32 compsInScan = info.compsInScan;
    
    // Precompute the decoding table for each table.
    
    HuffmanTable *ht [4];
    
  for (int32 curComp = 0; curComp < compsInScan; curComp++)
      {
      
        int32 ci = info.MCUmembership [curComp];
        
        JpegComponentInfo *compptr = info.curCompInfo [ci];
        
        ht [curComp] = info.dcHuffTblPtrs [compptr->dcTblNo];

      }
    
  MCU *prevRowBuf = mcuROW1;
  MCU *curRowBuf  = mcuROW2;
  
  #if qSupportCanon_sRAW
    
  // Canon sRAW support
  
  if (info.compInfo [0].hSampFactor == 2 &&
    info.compInfo [0].vSampFactor == 1)
    {
  
    for (int32 row = 0; row < numROW; row++)
      {
      
      // Initialize predictors.
      
      int32 p0;
      int32 p1;
      int32 p2;
      
      if (row == 0)
        {
        p0 = 1 << 14;
        p1 = 1 << 14;
        p2 = 1 << 14;
        }
        
      else
        {
        p0 = prevRowBuf [0] [0];
        p1 = prevRowBuf [0] [1];
        p2 = prevRowBuf [0] [2];
        }
      
      for (int32 col = 0; col < numCOL; col += 2)
        {
        
        // Read first luminance component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [0]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p0 += d;
          
          curRowBuf [col] [0] = (ComponentType) p0;
        
          }
        
        // Read second luminance component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [0]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p0 += d;
          
          curRowBuf [col + 1] [0] = (ComponentType) p0;
        
          }
        
        // Read first chroma component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [1]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p1 += d;
          
          curRowBuf [col    ] [1] = (ComponentType) p1;
          curRowBuf [col + 1] [1] = (ComponentType) p1;
        
          }
        
        // Read second chroma component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [2]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p2 += d;
          
          curRowBuf [col    ] [2] = (ComponentType) p2;
          curRowBuf [col + 1] [2] = (ComponentType) p2;
        
          }
                
        }
      
      PmPutRow (curRowBuf, compsInScan, numCOL, row);

      swap (MCU *, prevRowBuf, curRowBuf);
      
      }
      
    return;
    
    }
    
  if (info.compInfo [0].hSampFactor == 2 &&
    info.compInfo [0].vSampFactor == 2)
    {
  
    for (int32 row = 0; row < numROW; row += 2)
      {
      
      // Initialize predictors.
      
      int32 p0;
      int32 p1;
      int32 p2;
      
      if (row == 0)
        {
        p0 = 1 << 14;
        p1 = 1 << 14;
        p2 = 1 << 14;
        }
        
      else
        {
        p0 = prevRowBuf [0] [0];
        p1 = prevRowBuf [0] [1];
        p2 = prevRowBuf [0] [2];
        }
      
      for (int32 col = 0; col < numCOL; col += 2)
        {
        
        // Read first luminance component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [0]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p0 += d;
          
          prevRowBuf [col] [0] = (ComponentType) p0;
        
          }
        
        // Read second luminance component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [0]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p0 += d;
          
          prevRowBuf [col + 1] [0] = (ComponentType) p0;
        
          }
        
        // Read third luminance component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [0]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p0 += d;
          
          curRowBuf [col] [0] = (ComponentType) p0;
        
          }
        
        // Read fourth luminance component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [0]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p0 += d;
          
          curRowBuf [col + 1] [0] = (ComponentType) p0;
        
          }
        
        // Read first chroma component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [1]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p1 += d;
          
          prevRowBuf [col    ] [1] = (ComponentType) p1;
          prevRowBuf [col + 1] [1] = (ComponentType) p1;

          curRowBuf [col    ] [1] = (ComponentType) p1;
          curRowBuf [col + 1] [1] = (ComponentType) p1;
        
          }
        
        // Read second chroma component.
        
          {
        
          int32 d = 0;
        
          int32 s = HuffDecode (ht [2]);
          
          if (s)
            {

            if (s == 16)
              {
              d = -32768;
              }
            
            else
              {
              d = get_bits (s);
              HuffExtend (d, s);
              }

            }
            
          p2 += d;
          
          prevRowBuf [col    ] [2] = (ComponentType) p2;
          prevRowBuf [col + 1] [2] = (ComponentType) p2;
        
          curRowBuf [col    ] [2] = (ComponentType) p2;
          curRowBuf [col + 1] [2] = (ComponentType) p2;
        
          }
                
        }
      
      PmPutRow (prevRowBuf, compsInScan, numCOL, row);
      PmPutRow (curRowBuf, compsInScan, numCOL, row);

      }
      
    return;
    
    }

  #endif
  
  #if qSupportHasselblad_3FR
  
  if (info.Ss == 8 && (numCOL & 1) == 0)
    {
    
    fHasselblad3FR = true;
    
    for (int32 row = 0; row < numROW; row++)
      {
      
      int32 p0 = 32768;
      int32 p1 = 32768;
      
      for (int32 col = 0; col < numCOL; col += 2)
        {
        
        int32 s0 = HuffDecode (ht [0]);
        int32 s1 = HuffDecode (ht [0]);
        
        if (s0)
          {
          int32 d = get_bits (s0);
          if (s0 == 16)
            {
            d = -32768;
            }
          else
            {
            HuffExtend (d, s0);
            }
          p0 += d;
          }

        if (s1)
          {
          int32 d = get_bits (s1);
          if (s1 == 16)
            {
            d = -32768;
            }
          else
            {
            HuffExtend (d, s1);
            }
          p1 += d;
          }

        curRowBuf [col    ] [0] = (ComponentType) p0;
        curRowBuf [col + 1] [0] = (ComponentType) p1;
        
        }
      
      PmPutRow (curRowBuf, compsInScan, numCOL, row);

      }

    return;
    
    }
  
  #endif
  
    // Decode the first row of image. Output the row and
    // turn this row into a previous row for later predictor
    // calculation.

    DecodeFirstRow (mcuROW1);
    
    PmPutRow (mcuROW1, compsInScan, numCOL, 0);
    
  // Process each row.

    for (int32 row = 1; row < numROW; row++)
      {

        // Account for restart interval, process restart marker if needed.

    if (info.restartInRows)
      {
      
      if (info.restartRowsToGo == 0)
        {
        
        ProcessRestart ();
            
                // Reset predictors at restart.
                
        DecodeFirstRow (curRowBuf);
        
        PmPutRow (curRowBuf, compsInScan, numCOL, row);
        
        swap (MCU *, prevRowBuf, curRowBuf);
        
        continue;
        
              }
              
      info.restartRowsToGo--;
           
      }
      
    // The upper neighbors are predictors for the first column.

        for (int32 curComp = 0; curComp < compsInScan; curComp++)
          {
          
          // Section F.2.2.1: decode the difference

        int32 d = 0;
    
          int32 s = HuffDecode (ht [curComp]);
          
          if (s)
            {

            if (s == 16 && !fBug16)
              {
              d = -32768;
              }
            
            else
              {
          d = get_bits (s);
                HuffExtend (d, s);
                }

              }
              
          // First column of row above is predictor for first column.

            curRowBuf [0] [curComp] = (ComponentType) (d + prevRowBuf [0] [curComp]);
            
      }

        // For the rest of the column on this row, predictor
        // calculations are based on PSV. 

      if (compsInScan == 2 && info.Ss == 1 && numCOL > 1)
        {
        
        // This is the combination used by both the Canon and Kodak raw formats. 
        // Unrolling the general case logic results in a significant speed increase.
        
        uint16 *dPtr = &curRowBuf [1] [0];
        
        int32 prev0 = dPtr [-2];
        int32 prev1 = dPtr [-1];
        
      for (int32 col = 1; col < numCOL; col++)
            {
            
            int32 s = HuffDecode (ht [0]);
            
            if (s)
              {
              
              int32 d;

              if (s == 16 && !fBug16)
                {
                d = -32768;
                }
              
              else
                {
            d = get_bits (s);
                  HuffExtend (d, s);
                  }

              prev0 += d;
              
                }
                
            s = HuffDecode (ht [1]);
            
            if (s)
              {
              
              int32 d;

              if (s == 16 && !fBug16)
                {
                d = -32768;
                }
              
              else
                {
            d = get_bits (s);
                  HuffExtend (d, s);
                  }

          prev1 += d;
          
                }
            
        dPtr [0] = (uint16) prev0;
        dPtr [1] = (uint16) prev1;
        
        dPtr += 2;
        
            }
            
          }
          
        else
          {
          
      for (int32 col = 1; col < numCOL; col++)
            {
            
              for (int32 curComp = 0; curComp < compsInScan; curComp++)
                {
                
              // Section F.2.2.1: decode the difference

            int32 d = 0;
        
              int32 s = HuffDecode (ht [curComp]);
              
              if (s)
                {
                
                if (s == 16 && !fBug16)
                  {
                  d = -32768;
                  }
                
                else
                  {
              d = get_bits (s);
                    HuffExtend (d, s);
                    }

                  }
                  
              // Predict the pixel value.
                
                  int32 predictor = QuickPredict (col,
                                    curComp,
                                    curRowBuf,
                                    prevRowBuf);
                                  
                  // Save the difference.

                  curRowBuf [col] [curComp] = (ComponentType) (d + predictor);
                  
          }
          
        }

          }

    PmPutRow (curRowBuf, compsInScan, numCOL, row);
    
    swap (MCU *, prevRowBuf, curRowBuf);
    
      }
      
    #undef swap
  
  }

/*****************************************************************************/

void dng_lossless_decoder::StartRead (uint32 &imageWidth,
                      uint32 &imageHeight,
                      uint32 &imageChannels)
  { 
  
  ReadFileHeader    ();
  ReadScanHeader    ();
  DecoderStructInit ();
  HuffDecoderInit   ();
  
  imageWidth    = info.imageWidth;
  imageHeight   = info.imageHeight;
  imageChannels = info.compsInScan;
  
  }

/*****************************************************************************/

void dng_lossless_decoder::FinishRead ()
  {
  
  DecodeImage ();
    
  }

/*****************************************************************************/

void DecodeLosslessJPEG (dng_stream &stream,
               dng_spooler &spooler,
               uint32 minDecodedSize,
               uint32 maxDecodedSize,
             bool bug16)
  {
  
  dng_lossless_decoder decoder (&stream,
                    &spooler,
                    bug16);
  
  uint32 imageWidth;
  uint32 imageHeight;
  uint32 imageChannels;
  
  decoder.StartRead (imageWidth,
             imageHeight,
             imageChannels);
             
  uint32 decodedSize = imageWidth    *
             imageHeight   *
             imageChannels *
             (uint32) sizeof (uint16);
             
  if (decodedSize < minDecodedSize ||
    decodedSize > maxDecodedSize)
    {
    ThrowBadFormat ();
    }
  
  decoder.FinishRead ();
  
  }

/*****************************************************************************/

class dng_lossless_encoder
  {
  
  private:
  
    const uint16 *fSrcData;
    
    uint32 fSrcRows;
    uint32 fSrcCols;
    uint32 fSrcChannels;
    uint32 fSrcBitDepth;
    
    int32 fSrcRowStep;
    int32 fSrcColStep;
  
    dng_stream &fStream;
  
    HuffmanTable huffTable [4];
    
    uint32 freqCount [4] [257];
    
    // Current bit-accumulation buffer

    int32 huffPutBuffer;
    int32 huffPutBits;
    
    // Lookup table for number of bits in an 8 bit value.
    
    int numBitsTable [256];
    
  public:
  
    dng_lossless_encoder (const uint16 *srcData,
                  uint32 srcRows,
                  uint32 srcCols,
                  uint32 srcChannels,
                  uint32 srcBitDepth,
                  int32 srcRowStep,
                  int32 srcColStep,
                  dng_stream &stream);
    
    void Encode ();
    
  private:
  
    void EmitByte (uint8 value);
  
    void EmitBits (int code, int size);

    void FlushBits ();

    void CountOneDiff (int diff, uint32 *countTable);

    void EncodeOneDiff (int diff, HuffmanTable *dctbl);
    
    void FreqCountSet ();

    void HuffEncode ();

    void GenHuffCoding (HuffmanTable *htbl, uint32 *freq);

    void HuffOptimize ();

    void EmitMarker (JpegMarker mark);

    void Emit2bytes (int value);

    void EmitDht (int index);

    void EmitSof (JpegMarker code);

    void EmitSos ();

    void WriteFileHeader ();

    void WriteScanHeader ();

    void WriteFileTrailer ();

  };
  
/*****************************************************************************/

dng_lossless_encoder::dng_lossless_encoder (const uint16 *srcData,
                      uint32 srcRows,
                      uint32 srcCols,
                      uint32 srcChannels,
                      uint32 srcBitDepth,
                      int32 srcRowStep,
                      int32 srcColStep,
                      dng_stream &stream)
                    
  : fSrcData     (srcData    )
  , fSrcRows     (srcRows    )
  , fSrcCols     (srcCols    )
  , fSrcChannels (srcChannels)
  , fSrcBitDepth (srcBitDepth)
  , fSrcRowStep  (srcRowStep )
  , fSrcColStep  (srcColStep )
  , fStream      (stream     )
  
  , huffPutBuffer (0)
  , huffPutBits   (0)
  
  {
  
    // Initialize number of bits lookup table.
    
    numBitsTable [0] = 0;
      
    for (int i = 1; i < 256; i++)
      {
      
    int temp = i;
    int nbits = 1;
    
    while (temp >>= 1)
      {
        nbits++;
      }
      
    numBitsTable [i] = nbits;
    
      }
      
  }

/*****************************************************************************/

inline void dng_lossless_encoder::EmitByte (uint8 value)
  {
  
  fStream.Put_uint8 (value);
  
  }
  
/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * EmitBits --
 *
 *  Code for outputting bits to the file
 *
 *  Only the right 24 bits of huffPutBuffer are used; the valid
 *  bits are left-justified in this part.  At most 16 bits can be
 *  passed to EmitBits in one call, and we never retain more than 7
 *  bits in huffPutBuffer between calls, so 24 bits are
 *  sufficient.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  huffPutBuffer and huffPutBits are updated.
 *
 *--------------------------------------------------------------
 */
 
inline void dng_lossless_encoder::EmitBits (int code, int size)
  {
  
    DNG_ASSERT (size != 0, "Bad Huffman table entry");

    int putBits   = size;
  int putBuffer = code;
    
    putBits += huffPutBits;
    
    putBuffer <<= 24 - putBits;
    putBuffer |= huffPutBuffer;

    while (putBits >= 8)
      {
      
    uint8 c = (uint8) (putBuffer >> 16);

    // Output whole bytes we've accumulated with byte stuffing

    EmitByte (c);
    
    if (c == 0xFF)
      {
        EmitByte (0);
      }

    putBuffer <<= 8;
    putBits -= 8;
    
      }

    huffPutBuffer = putBuffer;
    huffPutBits   = putBits;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * FlushBits --
 *
 *  Flush any remaining bits in the bit buffer. Used before emitting
 *  a marker.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  huffPutBuffer and huffPutBits are reset
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::FlushBits ()
  {
  
    // The first call forces output of any partial bytes.

    EmitBits (0x007F, 7);
    
    // We can then zero the buffer.

    huffPutBuffer = 0;
    huffPutBits   = 0;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * CountOneDiff --
 *
 *      Count the difference value in countTable.
 *
 * Results:
 *      diff is counted in countTable.
 *
 * Side effects:
 *      None. 
 *
 *--------------------------------------------------------------
 */

inline void dng_lossless_encoder::CountOneDiff (int diff, uint32 *countTable)
  {
  
    // Encode the DC coefficient difference per section F.1.2.1
     
    int temp = diff;
    
    if (temp < 0)
      {
      
    temp = -temp;
 
      }

    // Find the number of bits needed for the magnitude of the coefficient

    int nbits = temp >= 256 ? numBitsTable [temp >> 8  ] + 8
                : numBitsTable [temp & 0xFF];
          
    // Update count for this bit length

    countTable [nbits] ++;
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * EncodeOneDiff --
 *
 *  Encode a single difference value.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

inline void dng_lossless_encoder::EncodeOneDiff (int diff, HuffmanTable *dctbl)
  {

    // Encode the DC coefficient difference per section F.1.2.1
     
    int temp  = diff;
    int temp2 = diff;
    
    if (temp < 0)
      {
      
    temp = -temp;
    
    // For a negative input, want temp2 = bitwise complement of
    // abs (input).  This code assumes we are on a two's complement
    // machine.

    temp2--;
    
      }

    // Find the number of bits needed for the magnitude of the coefficient

    int nbits = temp >= 256 ? numBitsTable [temp >> 8  ] + 8
                : numBitsTable [temp & 0xFF];

    // Emit the Huffman-coded symbol for the number of bits

    EmitBits (dctbl->ehufco [nbits],
          dctbl->ehufsi [nbits]);

    // Emit that number of bits of the value, if positive,
    // or the complement of its magnitude, if negative.
    
    // If the number of bits is 16, there is only one possible difference
    // value (-32786), so the lossless JPEG spec says not to output anything
    // in that case.  So we only need to output the diference value if
    // the number of bits is between 1 and 15.

    if (nbits & 15)
      {
      
    EmitBits (temp2 & (0x0FFFF >> (16 - nbits)),
          nbits);
    
    }

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * FreqCountSet --
 *
 *      Count the times each category symbol occurs in this image.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  The freqCount has counted all category 
 *  symbols appeared in the image.        
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::FreqCountSet ()
  {
    
  memset (freqCount, 0, sizeof (freqCount));
  
  DNG_ASSERT ((int32)fSrcRows >= 0, "dng_lossless_encoder::FreqCountSet: fSrcRpws too large.");

    for (int32 row = 0; row < (int32)fSrcRows; row++)
      {
      
    const uint16 *sPtr = fSrcData + row * fSrcRowStep;
    
    // Initialize predictors for this row.
    
    int32 predictor [4];
    
    for (int32 channel = 0; channel < (int32)fSrcChannels; channel++)
      {
      
      if (row == 0)
        predictor [channel] = 1 << (fSrcBitDepth - 1);
        
      else
        predictor [channel] = sPtr [channel - fSrcRowStep];
      
      }
      
    // Unroll most common case of two channels
    
    if (fSrcChannels == 2)
      {
      
      int32 pred0 = predictor [0];
      int32 pred1 = predictor [1];
      
      uint32 srcCols    = fSrcCols;
      int32  srcColStep = fSrcColStep;
      
        for (uint32 col = 0; col < srcCols; col++)
          {
          
          int32 pixel0 = sPtr [0];
        int32 pixel1 = sPtr [1];
          
          int16 diff0 = (int16) (pixel0 - pred0);
          int16 diff1 = (int16) (pixel1 - pred1);
          
          CountOneDiff (diff0, freqCount [0]);
          CountOneDiff (diff1, freqCount [1]);
          
          pred0 = pixel0;
          pred1 = pixel1;
            
          sPtr += srcColStep;
            
          }
      
      }
      
    // General case.
      
    else
      {
      
        for (uint32 col = 0; col < fSrcCols; col++)
          {
          
          for (uint32 channel = 0; channel < fSrcChannels; channel++)
            {
            
            int32 pixel = sPtr [channel];
            
            int16 diff = (int16) (pixel - predictor [channel]);
            
            CountOneDiff (diff, freqCount [channel]);
            
            predictor [channel] = pixel;
            
            }
            
          sPtr += fSrcColStep;
            
          }
          
        }
        
      }

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * HuffEncode --
 *
 *      Encode and output Huffman-compressed image data.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::HuffEncode ()
  {
    
  DNG_ASSERT ((int32)fSrcRows >= 0, "dng_lossless_encoder::HuffEncode: fSrcRows too large.");

  for (int32 row = 0; row < (int32)fSrcRows; row++)
      {
      
    const uint16 *sPtr = fSrcData + row * fSrcRowStep;
    
    // Initialize predictors for this row.
    
    int32 predictor [4];
    
    for (int32 channel = 0; channel < (int32)fSrcChannels; channel++)
      {
      
      if (row == 0)
        predictor [channel] = 1 << (fSrcBitDepth - 1);
        
      else
        predictor [channel] = sPtr [channel - fSrcRowStep];
      
      }
      
    // Unroll most common case of two channels
    
    if (fSrcChannels == 2)
      {
      
      int32 pred0 = predictor [0];
      int32 pred1 = predictor [1];
      
      uint32 srcCols    = fSrcCols;
      int32  srcColStep = fSrcColStep;
      
        for (uint32 col = 0; col < srcCols; col++)
          {
          
          int32 pixel0 = sPtr [0];
        int32 pixel1 = sPtr [1];
          
          int16 diff0 = (int16) (pixel0 - pred0);
          int16 diff1 = (int16) (pixel1 - pred1);
          
          EncodeOneDiff (diff0, &huffTable [0]);
          EncodeOneDiff (diff1, &huffTable [1]);
          
          pred0 = pixel0;
          pred1 = pixel1;
            
          sPtr += srcColStep;
            
          }
      
      }
      
    // General case.
      
    else
      {
      
        for (uint32 col = 0; col < fSrcCols; col++)
          {
          
          for (uint32 channel = 0; channel < fSrcChannels; channel++)
            {
            
            int32 pixel = sPtr [channel];
            
            int16 diff = (int16) (pixel - predictor [channel]);
            
            EncodeOneDiff (diff, &huffTable [channel]);
            
            predictor [channel] = pixel;
            
            }
            
          sPtr += fSrcColStep;
            
          }
          
        }
        
      }
  
    FlushBits ();
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * GenHuffCoding --
 *
 *  Generate the optimal coding for the given counts. 
 *  This algorithm is explained in section K.2 of the
 *  JPEG standard. 
 *
 * Results:
 *      htbl->bits and htbl->huffval are constructed.
 *
 * Side effects:
 *      None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::GenHuffCoding (HuffmanTable *htbl, uint32 *freq)
  {
  
  int i;
  int j;
  
  const int MAX_CLEN = 32;      // assumed maximum initial code length
  
  uint8 bits [MAX_CLEN + 1];  // bits [k] = # of symbols with code length k
  short codesize [257];     // codesize [k] = code length of symbol k
  short others   [257];     // next symbol in current branch of tree
  
  memset (bits    , 0, sizeof (bits    ));
    memset (codesize, 0, sizeof (codesize));
  
  for (i = 0; i < 257; i++)
    others [i] = -1;     // init links to empty

  // Including the pseudo-symbol 256 in the Huffman procedure guarantees
  // that no real symbol is given code-value of all ones, because 256
  // will be placed in the largest codeword category.

  freq [256] = 1;         // make sure there is a nonzero count

  // Huffman's basic algorithm to assign optimal code lengths to symbols
  
  while (true)
    {

    // Find the smallest nonzero frequency, set c1 = its symbol.
    // In case of ties, take the larger symbol number.

    int c1 = -1;
    
    uint32 v = 0xFFFFFFFF;
    
    for (i = 0; i <= 256; i++)
      {
      
      if (freq [i] && freq [i] <= v)
        {
        v = freq [i];
        c1 = i;
        }
  
      }

    // Find the next smallest nonzero frequency, set c2 = its symbol.
    // In case of ties, take the larger symbol number.

    int c2 = -1;
    
    v = 0xFFFFFFFF;
    
    for (i = 0; i <= 256; i++)
      {
      
          if (freq [i] && freq [i] <= v && i != c1) 
            {
        v = freq [i];
        c2 = i;
        }
        
      }

    // Done if we've merged everything into one frequency.

    if (c2 < 0)
          break;
    
    // Else merge the two counts/trees.

    freq [c1] += freq [c2];
    freq [c2] = 0;

    // Increment the codesize of everything in c1's tree branch.

    codesize [c1] ++;
    
    while (others [c1] >= 0)
      {
      c1 = others [c1];
      codesize [c1] ++;
        }
    
    // chain c2 onto c1's tree branch 

    others [c1] = (short) c2;
    
    // Increment the codesize of everything in c2's tree branch.

    codesize [c2] ++;
    
    while (others [c2] >= 0) 
      {
      c2 = others [c2];
      codesize [c2] ++;
      }

    }

  // Now count the number of symbols of each code length.

  for (i = 0; i <= 256; i++)
    {
    
    if (codesize [i])
      {

      // The JPEG standard seems to think that this can't happen,
      // but I'm paranoid...
      
      if (codesize [i] > MAX_CLEN)
        {
       
            DNG_REPORT ("Huffman code size table overflow");
            
            ThrowProgramError ();
            
            }

      bits [codesize [i]]++;
      
      }

    }

  // JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
  // Huffman procedure assigned any such lengths, we must adjust the coding.
  // Here is what the JPEG spec says about how this next bit works:
  // Since symbols are paired for the longest Huffman code, the symbols are
  // removed from this length category two at a time.  The prefix for the pair
  // (which is one bit shorter) is allocated to one of the pair; then,
  // skipping the BITS entry for that prefix length, a code word from the next
  // shortest nonzero BITS entry is converted into a prefix for two code words
  // one bit longer.
  
  for (i = MAX_CLEN; i > 16; i--)
    {
    
    while (bits [i] > 0)
      {
      
      // Kludge: I have never been able to test this logic, and there
      // are comments on the web that this encoder has bugs with 16-bit
      // data, so just throw an error if we get here and revert to a
      // default table.  - tknoll 12/1/03.
      
          DNG_REPORT ("Info: Optimal huffman table bigger than 16 bits");
          
      ThrowProgramError ();
      
      // Original logic:
      
      j = i - 2;    // find length of new prefix to be used
      
      while (bits [j] == 0)
        j--;
      
      bits [i    ] -= 2;    // remove two symbols
      bits [i - 1] ++;    // one goes in this length
      bits [j + 1] += 2;    // two new symbols in this length
      bits [j    ] --;    // symbol of this length is now a prefix
      
      }
      
    }

  // Remove the count for the pseudo-symbol 256 from
  // the largest codelength.
  
  while (bits [i] == 0)    // find largest codelength still in use
      i--;
      
  bits [i] --;
  
  // Return final symbol counts (only for lengths 0..16).

  memcpy (htbl->bits, bits, sizeof (htbl->bits));
  
  // Return a list of the symbols sorted by code length. 
  // It's not real clear to me why we don't need to consider the codelength
  // changes made above, but the JPEG spec seems to think this works.
   
  int p = 0;
  
  for (i = 1; i <= MAX_CLEN; i++)
    {
    
    for (j = 0; j <= 255; j++)
      {
      
      if (codesize [j] == i)
        {
        htbl->huffval [p] = (uint8) j;
        p++;
        }

        }
        
      }
 
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * HuffOptimize --
 *
 *  Find the best coding parameters for a Huffman-coded scan.
 *  When called, the scan data has already been converted to
 *  a sequence of MCU groups of source image samples, which
 *  are stored in a "big" array, mcuTable.
 *
 *  It counts the times each category symbol occurs. Based on
 *  this counting, optimal Huffman tables are built. Then it
 *  uses this optimal Huffman table and counting table to find
 *  the best PSV. 
 *
 * Results:
 *  Optimal Huffman tables are retured in cPtr->dcHuffTblPtrs[tbl].
 *  Best PSV is retured in cPtr->Ss.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::HuffOptimize ()
  {
  
    // Collect the frequency counts.
     
  FreqCountSet ();
  
  // Generate Huffman encoding tables.
  
  for (uint32 channel = 0; channel < fSrcChannels; channel++)
    {
    
    try
      {
      
          GenHuffCoding (&huffTable [channel], freqCount [channel]);
          
          }
          
        catch (...)
          {
          
          DNG_REPORT ("Info: Reverting to default huffman table");
          
          for (uint32 j = 0; j <= 256; j++)
            {
            
            freqCount [channel] [j] = (j <= 16 ? 1 : 0);
            
            }
          
          GenHuffCoding (&huffTable [channel], freqCount [channel]);
          
          }
        
        FixHuffTbl (&huffTable [channel]);
        
    }
 
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * EmitMarker --
 *
 *  Emit a marker code into the output stream.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::EmitMarker (JpegMarker mark)
  {
  
    EmitByte (0xFF);
    EmitByte ((uint8) mark);
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * Emit2bytes --
 *
 *  Emit a 2-byte integer; these are always MSB first in JPEG
 *  files
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::Emit2bytes (int value)
  {
  
    EmitByte ((value >> 8) & 0xFF);
    EmitByte (value & 0xFF);
 
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * EmitDht --
 *
 *  Emit a DHT marker, follwed by the huffman data.
 *
 * Results:
 *  None
 *
 * Side effects:
 *  None
 *
 *--------------------------------------------------------------
 */
 
void dng_lossless_encoder::EmitDht (int index)
  {
  
  int i;
  
    HuffmanTable *htbl = &huffTable [index];
    
  EmitMarker (M_DHT);

    int length = 0;
    
  for (i = 1; i <= 16; i++)
      length += htbl->bits [i];

  Emit2bytes (length + 2 + 1 + 16);
  
  EmitByte ((uint8) index);

  for (i = 1; i <= 16; i++)
      EmitByte (htbl->bits [i]);

  for (i = 0; i < length; i++)
      EmitByte (htbl->huffval [i]);

  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * EmitSof --
 *
 *  Emit a SOF marker plus data.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::EmitSof (JpegMarker code)
  {
  
    EmitMarker (code);

    Emit2bytes (3 * fSrcChannels + 2 + 5 + 1);  // length

    EmitByte ((uint8) fSrcBitDepth);
    
    Emit2bytes (fSrcRows);
    Emit2bytes (fSrcCols);

    EmitByte ((uint8) fSrcChannels);

    for (uint32 i = 0; i < fSrcChannels; i++)
      {
      
    EmitByte ((uint8) i);
    
    EmitByte ((uint8) ((1 << 4) + 1));    // Not subsampled.
           
        EmitByte (0);         // Tq shall be 0 for lossless.
        
      }
   
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * EmitSos --
 *
 *  Emit a SOS marker plus data.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::EmitSos ()
  {
  
    EmitMarker (M_SOS);

    Emit2bytes (2 * fSrcChannels + 2 + 1 + 3);  // length

    EmitByte ((uint8) fSrcChannels);      // Ns

    for (uint32 i = 0; i < fSrcChannels; i++) 
      { 
      
      // Cs,Td,Ta
      
    EmitByte ((uint8) i);
    EmitByte ((uint8) (i << 4));
    
      }

    EmitByte (1);   // PSV - hardcoded - tknoll
    EmitByte (0);     // Spectral selection end  - Se
    EmitByte (0);     // The point transform parameter 
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * WriteFileHeader --
 *
 *  Write the file header.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::WriteFileHeader ()
  {
  
    EmitMarker (M_SOI);   // first the SOI
    
    EmitSof (M_SOF3);
    
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * WriteScanHeader --
 *
 *  Write the start of a scan (everything through the SOS marker).
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::WriteScanHeader ()
  {

    // Emit Huffman tables.
    
    for (uint32 i = 0; i < fSrcChannels; i++)
      {
      
    EmitDht (i);
    
      }

  EmitSos ();
     
  }

/*****************************************************************************/

/*
 *--------------------------------------------------------------
 *
 * WriteFileTrailer --
 *
 *  Write the End of image marker at the end of a JPEG file.
 *
 * Results:
 *  None.
 *
 * Side effects:
 *  None.
 *
 *--------------------------------------------------------------
 */

void dng_lossless_encoder::WriteFileTrailer ()
  {
  
    EmitMarker (M_EOI);
    
  }

/*****************************************************************************/

void dng_lossless_encoder::Encode ()
  {
  
  DNG_ASSERT (fSrcChannels <= 4, "Too many components in scan");
    
  // Count the times each difference category occurs. 
  // Construct the optimal Huffman table.
    
  HuffOptimize ();

    // Write the frame and scan headers.

    WriteFileHeader (); 
    
    WriteScanHeader ();

    // Encode the image.
    
    HuffEncode ();

    // Clean up everything.
    
  WriteFileTrailer ();

  }

/*****************************************************************************/

void EncodeLosslessJPEG (const uint16 *srcData,
             uint32 srcRows,
             uint32 srcCols,
             uint32 srcChannels,
             uint32 srcBitDepth,
             int32 srcRowStep,
             int32 srcColStep,
             dng_stream &stream)
  {
  
  dng_lossless_encoder encoder (srcData,
                    srcRows,
                    srcCols,
                    srcChannels,
                    srcBitDepth,
                    srcRowStep,
                    srcColStep,
                    stream);

  encoder.Encode ();
  
    }

/*****************************************************************************/

Coverage Report

Created: 2025-11-16 06:25