/*

 * jdlossls.c

 *

 * This file was part of the Independent JPEG Group's software:

 * Copyright (C) 1998, Thomas G. Lane.

 * Lossless JPEG Modifications:

 * Copyright (C) 1999, Ken Murchison.

 * libjpeg-turbo Modifications:

 * Copyright (C) 2022, 2024, 2026, D. R. Commander.

 * For conditions of distribution and use, see the accompanying README.ijg

 * file.

 *

 * This file contains prediction, sample undifferencing, point transform, and

 * sample scaling routines for the lossless JPEG decompressor.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jlossls.h"

#ifdef D_LOSSLESS_SUPPORTED

/**************** Sample undifferencing (reconstruction) *****************/

/*

 * In order to avoid a performance penalty for checking which predictor is

 * being used and which row is being processed for each call of the

 * undifferencer, and to promote optimization, we have separate undifferencing

 * functions for each predictor selection value.

 *

 * We are able to avoid duplicating source code by implementing the predictors

 * and undifferencers as macros.  Each of the undifferencing functions is

 * simply a wrapper around an UNDIFFERENCE macro with the appropriate PREDICTOR

 * macro passed as an argument.

 */

/* Predictor for the first column of the first row: 2^(P-Pt-1) */

#define INITIAL_PREDICTORx  (1 << (cinfo->data_precision - cinfo->Al - 1))

/* Predictor for the first column of the remaining rows: Rb */

#define INITIAL_PREDICTOR2  prev_row[0]

/*

 * 1-Dimensional undifferencer routine.

 *

 * This macro implements the 1-D horizontal predictor (1).  INITIAL_PREDICTOR

 * is used as the special case predictor for the first column, which must be

 * either INITIAL_PREDICTOR2 or INITIAL_PREDICTORx.  The remaining samples

 * use PREDICTOR1.

 *

 * The reconstructed sample is supposed to be calculated modulo 2^16, so we

 * logically AND the result with 0xFFFF.

 */

#define UNDIFFERENCE_1D(INITIAL_PREDICTOR) \

  int Ra; \

  \

  Ra = (*diff_buf++ + INITIAL_PREDICTOR) & 0xFFFF; \

  *undiff_buf++ = Ra; \

  \

  while (--width) { \

    Ra = (*diff_buf++ + PREDICTOR1) & 0xFFFF; \

    *undiff_buf++ = Ra; \

  }

/*

 * 2-Dimensional undifferencer routine.

 *

 * This macro implements the 2-D horizontal predictors (#2-7).  PREDICTOR2 is

 * used as the special case predictor for the first column.  The remaining

 * samples use PREDICTOR, which is a function of Ra, Rb, and Rc.

 *

 * Because prev_row and output_buf may point to the same storage area (in an

 * interleaved image with Vi=1, for example), we must take care to buffer Rb/Rc

 * before writing the current reconstructed sample value into output_buf.

 *

 * The reconstructed sample is supposed to be calculated modulo 2^16, so we

 * logically AND the result with 0xFFFF.

 */

#define UNDIFFERENCE_2D(PREDICTOR) \

  int Ra, Rb, Rc; \

  \

  Rb = *prev_row++; \

  Ra = (*diff_buf++ + PREDICTOR2) & 0xFFFF; \

  *undiff_buf++ = Ra; \

  \

  while (--width) { \

    Rc = Rb; \

    Rb = *prev_row++; \

    Ra = (*diff_buf++ + PREDICTOR) & 0xFFFF; \

    *undiff_buf++ = Ra; \

  }

/*

 * Undifferencers for the second and subsequent rows in a scan or restart

 * interval.  The first sample in the row is undifferenced using the vertical

 * predictor (2).  The rest of the samples are undifferenced using the

 * predictor specified in the scan header.

 */

METHODDEF(void)

jpeg_undifference1(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_1D(INITIAL_PREDICTOR2);

}

METHODDEF(void)

jpeg_undifference2(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_2D(PREDICTOR2);

  (void)(Rc);

}

METHODDEF(void)

jpeg_undifference3(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_2D(PREDICTOR3);

}

METHODDEF(void)

jpeg_undifference4(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_2D(PREDICTOR4);

}

METHODDEF(void)

jpeg_undifference5(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_2D(PREDICTOR5);

}

METHODDEF(void)

jpeg_undifference6(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_2D(PREDICTOR6);

}

METHODDEF(void)

jpeg_undifference7(j_decompress_ptr cinfo, int comp_index,

                   JDIFFROW diff_buf, JDIFFROW prev_row,

                   JDIFFROW undiff_buf, JDIMENSION width)

{

  UNDIFFERENCE_2D(PREDICTOR7);

  (void)(Rc);

}

/*

 * Undifferencer for the first row in a scan or restart interval.  The first

 * sample in the row is undifferenced using the special predictor constant

 * x=2^(P-Pt-1).  The rest of the samples are undifferenced using the

 * 1-D horizontal predictor (1).

 */

METHODDEF(void)

jpeg_undifference_first_row(j_decompress_ptr cinfo, int comp_index,

                            JDIFFROW diff_buf, JDIFFROW prev_row,

                            JDIFFROW undiff_buf, JDIMENSION width)

{

  lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;

  UNDIFFERENCE_1D(INITIAL_PREDICTORx);

  /*

   * Now that we have undifferenced the first row, we want to use the

   * undifferencer that corresponds to the predictor specified in the

   * scan header.

   */

  switch (cinfo->Ss) {

  case 1:

    losslessd->predict_undifference[comp_index] = jpeg_undifference1;

    break;

  case 2:

    losslessd->predict_undifference[comp_index] = jpeg_undifference2;

    break;

  case 3:

    losslessd->predict_undifference[comp_index] = jpeg_undifference3;

    break;

  case 4:

    losslessd->predict_undifference[comp_index] = jpeg_undifference4;

    break;

  case 5:

    losslessd->predict_undifference[comp_index] = jpeg_undifference5;

    break;

  case 6:

    losslessd->predict_undifference[comp_index] = jpeg_undifference6;

    break;

  case 7:

    losslessd->predict_undifference[comp_index] = jpeg_undifference7;

    break;

  default:

    ERREXIT4(cinfo, JERR_BAD_PROGRESSION,

             cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

  }

}

/*********************** Sample upscaling by 2^Pt ************************/

METHODDEF(void)

simple_upscale(j_decompress_ptr cinfo,

               JDIFFROW diff_buf, _JSAMPROW output_buf, JDIMENSION width)

{

  do {

    *output_buf++ = (_JSAMPLE)(*diff_buf++ << cinfo->Al);

  } while (--width);

}

METHODDEF(void)

noscale(j_decompress_ptr cinfo,

        JDIFFROW diff_buf, _JSAMPROW output_buf, JDIMENSION width)

{

  do {

    *output_buf++ = (_JSAMPLE)(*diff_buf++);

  } while (--width);

}

/*

 * Initialize for an input processing pass.

 */

METHODDEF(void)

start_pass_lossless(j_decompress_ptr cinfo)

{

  lossless_decomp_ptr losslessd = (lossless_decomp_ptr)cinfo->idct;

  int ci;

  /* Check that the scan parameters Ss, Se, Ah, Al are OK for lossless JPEG.

   *

   * Ss is the predictor selection value (psv).  Legal values for sequential

   * lossless JPEG are: 1 <= psv <= 7.

   *

   * Se and Ah are not used and should be zero.

   *

   * Al specifies the point transform (Pt).

   * Legal values are: 0 <= Pt <= (data precision - 1).

   */

  if (cinfo->Ss < 1 || cinfo->Ss > 7 ||

      cinfo->Se != 0 || cinfo->Ah != 0 ||

      cinfo->Al < 0 || cinfo->Al >= cinfo->data_precision)

    ERREXIT4(cinfo, JERR_BAD_PROGRESSION,

             cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

  /* Set undifference functions to first row function */

  for (ci = 0; ci < cinfo->num_components; ci++)

    losslessd->predict_undifference[ci] = jpeg_undifference_first_row;

  /* Set scaler function based on Pt */

  if (cinfo->Al)

    losslessd->scaler_scale = simple_upscale;

  else

    losslessd->scaler_scale = noscale;

}

/*

 * Initialize the lossless decompressor.

 */

GLOBAL(void)

_jinit_lossless_decompressor(j_decompress_ptr cinfo)

{

  lossless_decomp_ptr losslessd;

#if BITS_IN_JSAMPLE == 8

  if (cinfo->data_precision > BITS_IN_JSAMPLE || cinfo->data_precision < 2)

#else

  if (cinfo->data_precision > BITS_IN_JSAMPLE ||

      cinfo->data_precision < BITS_IN_JSAMPLE - 3)

#endif

    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);

  /* Create subobject in permanent pool */

  losslessd = (lossless_decomp_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,

                                sizeof(jpeg_lossless_decompressor));

  cinfo->idct = (struct jpeg_inverse_dct *)losslessd;

  losslessd->pub.start_pass = start_pass_lossless;

}

#endif /* D_LOSSLESS_SUPPORTED */