kc3-lang/libjpeg-turbo/src/jdmaster.c

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• Hash : 9758c8a7
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  Date : 2024-11-18T13:40:08
  

  Exclude more code if !(C|D)_LOSSLESS_SUPPORTED
  

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• src/jdmaster.c

• /*
   * jdmaster.c
   *
   * This file was part of the Independent JPEG Group's software:
   * Copyright (C) 1991-1997, Thomas G. Lane.
   * Modified 2002-2009 by Guido Vollbeding.
   * Lossless JPEG Modifications:
   * Copyright (C) 1999, Ken Murchison.
   * libjpeg-turbo Modifications:
   * Copyright (C) 2009-2011, 2016, 2019, 2022-2024, D. R. Commander.
   * Copyright (C) 2013, Linaro Limited.
   * Copyright (C) 2015, Google, Inc.
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   *
   * This file contains master control logic for the JPEG decompressor.
   * These routines are concerned with selecting the modules to be executed
   * and with determining the number of passes and the work to be done in each
   * pass.
   */
  
  #define JPEG_INTERNALS
  #include "jinclude.h"
  #include "jpeglib.h"
  #include "jpegapicomp.h"
  #include "jdmaster.h"
  
  
  /*
   * Determine whether merged upsample/color conversion should be used.
   * CRUCIAL: this must match the actual capabilities of jdmerge.c!
   */
  
  LOCAL(boolean)
  use_merged_upsample(j_decompress_ptr cinfo)
  {
  #ifdef UPSAMPLE_MERGING_SUPPORTED
    /* Colorspace conversion is not supported with lossless JPEG images */
    if (cinfo->master->lossless)
      return FALSE;
    /* Merging is the equivalent of plain box-filter upsampling */
    if (cinfo->do_fancy_upsampling || cinfo->CCIR601_sampling)
      return FALSE;
    /* jdmerge.c only supports YCC=>RGB and YCC=>RGB565 color conversion */
    if (cinfo->jpeg_color_space != JCS_YCbCr || cinfo->num_components != 3 ||
        (cinfo->out_color_space != JCS_RGB &&
         cinfo->out_color_space != JCS_RGB565 &&
         cinfo->out_color_space != JCS_EXT_RGB &&
         cinfo->out_color_space != JCS_EXT_RGBX &&
         cinfo->out_color_space != JCS_EXT_BGR &&
         cinfo->out_color_space != JCS_EXT_BGRX &&
         cinfo->out_color_space != JCS_EXT_XBGR &&
         cinfo->out_color_space != JCS_EXT_XRGB &&
         cinfo->out_color_space != JCS_EXT_RGBA &&
         cinfo->out_color_space != JCS_EXT_BGRA &&
         cinfo->out_color_space != JCS_EXT_ABGR &&
         cinfo->out_color_space != JCS_EXT_ARGB))
      return FALSE;
    if ((cinfo->out_color_space == JCS_RGB565 &&
         cinfo->out_color_components != 3) ||
        (cinfo->out_color_space != JCS_RGB565 &&
         cinfo->out_color_components != rgb_pixelsize[cinfo->out_color_space]))
      return FALSE;
    /* and it only handles 2h1v or 2h2v sampling ratios */
    if (cinfo->comp_info[0].h_samp_factor != 2 ||
        cinfo->comp_info[1].h_samp_factor != 1 ||
        cinfo->comp_info[2].h_samp_factor != 1 ||
        cinfo->comp_info[0].v_samp_factor >  2 ||
        cinfo->comp_info[1].v_samp_factor != 1 ||
        cinfo->comp_info[2].v_samp_factor != 1)
      return FALSE;
    /* furthermore, it doesn't work if we've scaled the IDCTs differently */
    if (cinfo->comp_info[0]._DCT_scaled_size != cinfo->_min_DCT_scaled_size ||
        cinfo->comp_info[1]._DCT_scaled_size != cinfo->_min_DCT_scaled_size ||
        cinfo->comp_info[2]._DCT_scaled_size != cinfo->_min_DCT_scaled_size)
      return FALSE;
    /* ??? also need to test for upsample-time rescaling, when & if supported */
    return TRUE;                  /* by golly, it'll work... */
  #else
    return FALSE;
  #endif
  }
  
  
  /*
   * Compute output image dimensions and related values.
   * NOTE: this is exported for possible use by application.
   * Hence it mustn't do anything that can't be done twice.
   */
  
  #if JPEG_LIB_VERSION >= 80
  GLOBAL(void)
  #else
  LOCAL(void)
  #endif
  jpeg_core_output_dimensions(j_decompress_ptr cinfo)
  /* Do computations that are needed before master selection phase.
   * This function is used for transcoding and full decompression.
   */
  {
  #ifdef IDCT_SCALING_SUPPORTED
    int ci;
    jpeg_component_info *compptr;
  
    if (!cinfo->master->lossless) {
      /* Compute actual output image dimensions and DCT scaling choices. */
      if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom) {
        /* Provide 1/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 1;
        cinfo->_min_DCT_v_scaled_size = 1;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 2) {
        /* Provide 2/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 2L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 2L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 2;
        cinfo->_min_DCT_v_scaled_size = 2;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 3) {
        /* Provide 3/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 3L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 3L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 3;
        cinfo->_min_DCT_v_scaled_size = 3;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 4) {
        /* Provide 4/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 4L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 4L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 4;
        cinfo->_min_DCT_v_scaled_size = 4;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 5) {
        /* Provide 5/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 5L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 5L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 5;
        cinfo->_min_DCT_v_scaled_size = 5;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 6) {
        /* Provide 6/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 6L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 6L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 6;
        cinfo->_min_DCT_v_scaled_size = 6;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 7) {
        /* Provide 7/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 7L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 7L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 7;
        cinfo->_min_DCT_v_scaled_size = 7;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 8) {
        /* Provide 8/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 8L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 8L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 8;
        cinfo->_min_DCT_v_scaled_size = 8;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 9) {
        /* Provide 9/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 9L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 9L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 9;
        cinfo->_min_DCT_v_scaled_size = 9;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 10) {
        /* Provide 10/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 10L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 10L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 10;
        cinfo->_min_DCT_v_scaled_size = 10;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 11) {
        /* Provide 11/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 11L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 11L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 11;
        cinfo->_min_DCT_v_scaled_size = 11;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 12) {
        /* Provide 12/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 12L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 12L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 12;
        cinfo->_min_DCT_v_scaled_size = 12;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 13) {
        /* Provide 13/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 13L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 13L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 13;
        cinfo->_min_DCT_v_scaled_size = 13;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 14) {
        /* Provide 14/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 14L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 14L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 14;
        cinfo->_min_DCT_v_scaled_size = 14;
      } else if (cinfo->scale_num * DCTSIZE <= cinfo->scale_denom * 15) {
        /* Provide 15/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 15L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 15L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 15;
        cinfo->_min_DCT_v_scaled_size = 15;
      } else {
        /* Provide 16/block_size scaling */
        cinfo->output_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width * 16L, (long)DCTSIZE);
        cinfo->output_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height * 16L, (long)DCTSIZE);
        cinfo->_min_DCT_h_scaled_size = 16;
        cinfo->_min_DCT_v_scaled_size = 16;
      }
  
      /* Recompute dimensions of components */
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
           ci++, compptr++) {
        compptr->_DCT_h_scaled_size = cinfo->_min_DCT_h_scaled_size;
        compptr->_DCT_v_scaled_size = cinfo->_min_DCT_v_scaled_size;
      }
    } else
  #endif /* !IDCT_SCALING_SUPPORTED */
    {
      /* Hardwire it to "no scaling" */
      cinfo->output_width = cinfo->image_width;
      cinfo->output_height = cinfo->image_height;
      /* jdinput.c has already initialized DCT_scaled_size,
       * and has computed unscaled downsampled_width and downsampled_height.
       */
    }
  }
  
  
  /*
   * Compute output image dimensions and related values.
   * NOTE: this is exported for possible use by application.
   * Hence it mustn't do anything that can't be done twice.
   * Also note that it may be called before the master module is initialized!
   */
  
  GLOBAL(void)
  jpeg_calc_output_dimensions(j_decompress_ptr cinfo)
  /* Do computations that are needed before master selection phase */
  {
  #ifdef IDCT_SCALING_SUPPORTED
    int ci;
    jpeg_component_info *compptr;
  #endif
  
    /* Prevent application from calling me at wrong times */
    if (cinfo->global_state != DSTATE_READY)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    /* Compute core output image dimensions and DCT scaling choices. */
    jpeg_core_output_dimensions(cinfo);
  
  #ifdef IDCT_SCALING_SUPPORTED
  
    if (!cinfo->master->lossless) {
      /* In selecting the actual DCT scaling for each component, we try to
       * scale up the chroma components via IDCT scaling rather than upsampling.
       * This saves time if the upsampler gets to use 1:1 scaling.
       * Note this code adapts subsampling ratios which are powers of 2.
       */
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
           ci++, compptr++) {
        int ssize = cinfo->_min_DCT_scaled_size;
        while (ssize < DCTSIZE &&
               ((cinfo->max_h_samp_factor * cinfo->_min_DCT_scaled_size) %
                (compptr->h_samp_factor * ssize * 2) == 0) &&
               ((cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size) %
                (compptr->v_samp_factor * ssize * 2) == 0)) {
          ssize = ssize * 2;
        }
  #if JPEG_LIB_VERSION >= 70
        compptr->DCT_h_scaled_size = compptr->DCT_v_scaled_size = ssize;
  #else
        compptr->DCT_scaled_size = ssize;
  #endif
      }
  
      /* Recompute downsampled dimensions of components;
       * application needs to know these if using raw downsampled data.
       */
      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
           ci++, compptr++) {
        /* Size in samples, after IDCT scaling */
        compptr->downsampled_width = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_width *
                        (long)(compptr->h_samp_factor *
                               compptr->_DCT_scaled_size),
                        (long)(cinfo->max_h_samp_factor * DCTSIZE));
        compptr->downsampled_height = (JDIMENSION)
          jdiv_round_up((long)cinfo->image_height *
                        (long)(compptr->v_samp_factor *
                               compptr->_DCT_scaled_size),
                        (long)(cinfo->max_v_samp_factor * DCTSIZE));
      }
    } else
  #endif /* IDCT_SCALING_SUPPORTED */
    {
      /* Hardwire it to "no scaling" */
      cinfo->output_width = cinfo->image_width;
      cinfo->output_height = cinfo->image_height;
      /* jdinput.c has already initialized DCT_scaled_size to DCTSIZE,
       * and has computed unscaled downsampled_width and downsampled_height.
       */
    }
  
    /* Report number of components in selected colorspace. */
    /* Probably this should be in the color conversion module... */
    switch (cinfo->out_color_space) {
    case JCS_GRAYSCALE:
      cinfo->out_color_components = 1;
      break;
    case JCS_RGB:
    case JCS_EXT_RGB:
    case JCS_EXT_RGBX:
    case JCS_EXT_BGR:
    case JCS_EXT_BGRX:
    case JCS_EXT_XBGR:
    case JCS_EXT_XRGB:
    case JCS_EXT_RGBA:
    case JCS_EXT_BGRA:
    case JCS_EXT_ABGR:
    case JCS_EXT_ARGB:
      cinfo->out_color_components = rgb_pixelsize[cinfo->out_color_space];
      break;
    case JCS_YCbCr:
    case JCS_RGB565:
      cinfo->out_color_components = 3;
      break;
    case JCS_CMYK:
    case JCS_YCCK:
      cinfo->out_color_components = 4;
      break;
    default:                      /* else must be same colorspace as in file */
      cinfo->out_color_components = cinfo->num_components;
      break;
    }
    cinfo->output_components = (cinfo->quantize_colors ? 1 :
                                cinfo->out_color_components);
  
    /* See if upsampler will want to emit more than one row at a time */
    if (use_merged_upsample(cinfo))
      cinfo->rec_outbuf_height = cinfo->max_v_samp_factor;
    else
      cinfo->rec_outbuf_height = 1;
  }
  
  
  /*
   * Several decompression processes need to range-limit values to the range
   * 0..MAXJSAMPLE; the input value may fall somewhat outside this range
   * due to noise introduced by quantization, roundoff error, etc.  These
   * processes are inner loops and need to be as fast as possible.  On most
   * machines, particularly CPUs with pipelines or instruction prefetch,
   * a (subscript-check-less) C table lookup
   *              x = sample_range_limit[x];
   * is faster than explicit tests
   *              if (x < 0)  x = 0;
   *              else if (x > MAXJSAMPLE)  x = MAXJSAMPLE;
   * These processes all use a common table prepared by the routine below.
   *
   * For most steps we can mathematically guarantee that the initial value
   * of x is within MAXJSAMPLE+1 of the legal range, so a table running from
   * -(MAXJSAMPLE+1) to 2*MAXJSAMPLE+1 is sufficient.  But for the initial
   * limiting step (just after the IDCT), a wildly out-of-range value is
   * possible if the input data is corrupt.  To avoid any chance of indexing
   * off the end of memory and getting a bad-pointer trap, we perform the
   * post-IDCT limiting thus:
   *              x = range_limit[x & MASK];
   * where MASK is 2 bits wider than legal sample data, ie 10 bits for 8-bit
   * samples.  Under normal circumstances this is more than enough range and
   * a correct output will be generated; with bogus input data the mask will
   * cause wraparound, and we will safely generate a bogus-but-in-range output.
   * For the post-IDCT step, we want to convert the data from signed to unsigned
   * representation by adding CENTERJSAMPLE at the same time that we limit it.
   * So the post-IDCT limiting table ends up looking like this:
   *   CENTERJSAMPLE,CENTERJSAMPLE+1,...,MAXJSAMPLE,
   *   MAXJSAMPLE (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
   *   0          (repeat 2*(MAXJSAMPLE+1)-CENTERJSAMPLE times),
   *   0,1,...,CENTERJSAMPLE-1
   * Negative inputs select values from the upper half of the table after
   * masking.
   *
   * We can save some space by overlapping the start of the post-IDCT table
   * with the simpler range limiting table.  The post-IDCT table begins at
   * sample_range_limit + CENTERJSAMPLE.
   */
  
  LOCAL(void)
  prepare_range_limit_table(j_decompress_ptr cinfo)
  /* Allocate and fill in the sample_range_limit table */
  {
    JSAMPLE *table;
    J12SAMPLE *table12;
  #ifdef D_LOSSLESS_SUPPORTED
    J16SAMPLE *table16;
  #endif
    int i;
  
    if (cinfo->data_precision <= 8) {
      table = (JSAMPLE *)
        (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                    (5 * (MAXJSAMPLE + 1) + CENTERJSAMPLE) * sizeof(JSAMPLE));
      table += (MAXJSAMPLE + 1);  /* allow negative subscripts of simple table */
      cinfo->sample_range_limit = table;
      /* First segment of "simple" table: limit[x] = 0 for x < 0 */
      memset(table - (MAXJSAMPLE + 1), 0, (MAXJSAMPLE + 1) * sizeof(JSAMPLE));
      /* Main part of "simple" table: limit[x] = x */
      for (i = 0; i <= MAXJSAMPLE; i++)
        table[i] = (JSAMPLE)i;
      table += CENTERJSAMPLE;     /* Point to where post-IDCT table starts */
      /* End of simple table, rest of first half of post-IDCT table */
      for (i = CENTERJSAMPLE; i < 2 * (MAXJSAMPLE + 1); i++)
        table[i] = MAXJSAMPLE;
      /* Second half of post-IDCT table */
      memset(table + (2 * (MAXJSAMPLE + 1)), 0,
             (2 * (MAXJSAMPLE + 1) - CENTERJSAMPLE) * sizeof(JSAMPLE));
      memcpy(table + (4 * (MAXJSAMPLE + 1) - CENTERJSAMPLE),
             cinfo->sample_range_limit, CENTERJSAMPLE * sizeof(JSAMPLE));
    } else if (cinfo->data_precision <= 12) {
      table12 = (J12SAMPLE *)
        (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                    (5 * (MAXJ12SAMPLE + 1) + CENTERJ12SAMPLE) *
                    sizeof(J12SAMPLE));
      table12 += (MAXJ12SAMPLE + 1);  /* allow negative subscripts of simple
                                         table */
      cinfo->sample_range_limit = (JSAMPLE *)table12;
      /* First segment of "simple" table: limit[x] = 0 for x < 0 */
      memset(table12 - (MAXJ12SAMPLE + 1), 0,
             (MAXJ12SAMPLE + 1) * sizeof(J12SAMPLE));
      /* Main part of "simple" table: limit[x] = x */
      for (i = 0; i <= MAXJ12SAMPLE; i++)
        table12[i] = (J12SAMPLE)i;
      table12 += CENTERJ12SAMPLE; /* Point to where post-IDCT table starts */
      /* End of simple table, rest of first half of post-IDCT table */
      for (i = CENTERJ12SAMPLE; i < 2 * (MAXJ12SAMPLE + 1); i++)
        table12[i] = MAXJ12SAMPLE;
      /* Second half of post-IDCT table */
      memset(table12 + (2 * (MAXJ12SAMPLE + 1)), 0,
             (2 * (MAXJ12SAMPLE + 1) - CENTERJ12SAMPLE) * sizeof(J12SAMPLE));
      memcpy(table12 + (4 * (MAXJ12SAMPLE + 1) - CENTERJ12SAMPLE),
             cinfo->sample_range_limit, CENTERJ12SAMPLE * sizeof(J12SAMPLE));
    } else {
  #ifdef D_LOSSLESS_SUPPORTED
      table16 = (J16SAMPLE *)
        (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                    (5 * (MAXJ16SAMPLE + 1) + CENTERJ16SAMPLE) *
                    sizeof(J16SAMPLE));
      table16 += (MAXJ16SAMPLE + 1);  /* allow negative subscripts of simple
                                         table */
      cinfo->sample_range_limit = (JSAMPLE *)table16;
      /* First segment of "simple" table: limit[x] = 0 for x < 0 */
      memset(table16 - (MAXJ16SAMPLE + 1), 0,
             (MAXJ16SAMPLE + 1) * sizeof(J16SAMPLE));
      /* Main part of "simple" table: limit[x] = x */
      for (i = 0; i <= MAXJ16SAMPLE; i++)
        table16[i] = (J16SAMPLE)i;
      table16 += CENTERJ16SAMPLE; /* Point to where post-IDCT table starts */
      /* End of simple table, rest of first half of post-IDCT table */
      for (i = CENTERJ16SAMPLE; i < 2 * (MAXJ16SAMPLE + 1); i++)
        table16[i] = MAXJ16SAMPLE;
      /* Second half of post-IDCT table */
      memset(table16 + (2 * (MAXJ16SAMPLE + 1)), 0,
             (2 * (MAXJ16SAMPLE + 1) - CENTERJ16SAMPLE) * sizeof(J16SAMPLE));
      memcpy(table16 + (4 * (MAXJ16SAMPLE + 1) - CENTERJ16SAMPLE),
             cinfo->sample_range_limit, CENTERJ16SAMPLE * sizeof(J16SAMPLE));
  #else
      ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  #endif
    }
  }
  
  
  /*
   * Master selection of decompression modules.
   * This is done once at jpeg_start_decompress time.  We determine
   * which modules will be used and give them appropriate initialization calls.
   * We also initialize the decompressor input side to begin consuming data.
   *
   * Since jpeg_read_header has finished, we know what is in the SOF
   * and (first) SOS markers.  We also have all the application parameter
   * settings.
   */
  
  LOCAL(void)
  master_selection(j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr)cinfo->master;
    boolean use_c_buffer;
    long samplesperrow;
    JDIMENSION jd_samplesperrow;
  
    /* Disable IDCT scaling and raw (downsampled) data output in lossless mode.
     * IDCT scaling is not useful in lossless mode, and it must be disabled in
     * order to properly calculate the output dimensions.  Raw data output isn't
     * particularly useful without subsampling and has not been tested in
     * lossless mode.
     */
  #ifdef D_LOSSLESS_SUPPORTED
    if (cinfo->master->lossless) {
      cinfo->raw_data_out = FALSE;
      cinfo->scale_num = cinfo->scale_denom = 1;
    }
  #endif
  
    /* Initialize dimensions and other stuff */
    jpeg_calc_output_dimensions(cinfo);
    prepare_range_limit_table(cinfo);
  
    /* Width of an output scanline must be representable as JDIMENSION. */
    samplesperrow = (long)cinfo->output_width *
                    (long)cinfo->out_color_components;
    jd_samplesperrow = (JDIMENSION)samplesperrow;
    if ((long)jd_samplesperrow != samplesperrow)
      ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
  
    /* Initialize my private state */
    master->pass_number = 0;
    master->using_merged_upsample = use_merged_upsample(cinfo);
  
    /* Color quantizer selection */
    master->quantizer_1pass = NULL;
    master->quantizer_2pass = NULL;
    /* No mode changes if not using buffered-image mode. */
    if (!cinfo->quantize_colors || !cinfo->buffered_image) {
      cinfo->enable_1pass_quant = FALSE;
      cinfo->enable_external_quant = FALSE;
      cinfo->enable_2pass_quant = FALSE;
    }
    if (cinfo->quantize_colors) {
      if (cinfo->raw_data_out)
        ERREXIT(cinfo, JERR_NOTIMPL);
      /* 2-pass quantizer only works in 3-component color space. */
      if (cinfo->out_color_components != 3 ||
          cinfo->out_color_space == JCS_RGB565) {
        cinfo->enable_1pass_quant = TRUE;
        cinfo->enable_external_quant = FALSE;
        cinfo->enable_2pass_quant = FALSE;
        cinfo->colormap = NULL;
      } else if (cinfo->colormap != NULL) {
        cinfo->enable_external_quant = TRUE;
      } else if (cinfo->two_pass_quantize) {
        cinfo->enable_2pass_quant = TRUE;
      } else {
        cinfo->enable_1pass_quant = TRUE;
      }
  
      if (cinfo->enable_1pass_quant) {
  #ifdef QUANT_1PASS_SUPPORTED
        if (cinfo->data_precision == 8)
          jinit_1pass_quantizer(cinfo);
        else if (cinfo->data_precision == 12)
          j12init_1pass_quantizer(cinfo);
        else
          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
        master->quantizer_1pass = cinfo->cquantize;
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      }
  
      /* We use the 2-pass code to map to external colormaps. */
      if (cinfo->enable_2pass_quant || cinfo->enable_external_quant) {
  #ifdef QUANT_2PASS_SUPPORTED
        if (cinfo->data_precision == 8)
          jinit_2pass_quantizer(cinfo);
        else if (cinfo->data_precision == 12)
          j12init_2pass_quantizer(cinfo);
        else
          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
        master->quantizer_2pass = cinfo->cquantize;
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      }
      /* If both quantizers are initialized, the 2-pass one is left active;
       * this is necessary for starting with quantization to an external map.
       */
    }
  
    /* Post-processing: in particular, color conversion first */
    if (!cinfo->raw_data_out) {
      if (master->using_merged_upsample) {
  #ifdef UPSAMPLE_MERGING_SUPPORTED
        if (cinfo->data_precision == 8)
          jinit_merged_upsampler(cinfo); /* does color conversion too */
        else if (cinfo->data_precision == 12)
          j12init_merged_upsampler(cinfo); /* does color conversion too */
        else
          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  #else
        ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
      } else {
        if (cinfo->data_precision <= 8) {
          jinit_color_deconverter(cinfo);
          jinit_upsampler(cinfo);
        } else if (cinfo->data_precision <= 12) {
          j12init_color_deconverter(cinfo);
          j12init_upsampler(cinfo);
        } else {
  #ifdef D_LOSSLESS_SUPPORTED
          j16init_color_deconverter(cinfo);
          j16init_upsampler(cinfo);
  #else
          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  #endif
        }
      }
      if (cinfo->data_precision <= 8)
        jinit_d_post_controller(cinfo, cinfo->enable_2pass_quant);
      else if (cinfo->data_precision <= 12)
        j12init_d_post_controller(cinfo, cinfo->enable_2pass_quant);
      else
  #ifdef D_LOSSLESS_SUPPORTED
        j16init_d_post_controller(cinfo, cinfo->enable_2pass_quant);
  #else
        ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  #endif
    }
  
    if (cinfo->master->lossless) {
  #ifdef D_LOSSLESS_SUPPORTED
      /* Prediction, sample undifferencing, point transform, and sample size
       * scaling
       */
      if (cinfo->data_precision <= 8)
        jinit_lossless_decompressor(cinfo);
      else if (cinfo->data_precision <= 12)
        j12init_lossless_decompressor(cinfo);
      else
        j16init_lossless_decompressor(cinfo);
      /* Entropy decoding: either Huffman or arithmetic coding. */
      if (cinfo->arith_code) {
        ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
      } else {
        jinit_lhuff_decoder(cinfo);
      }
  
      /* Initialize principal buffer controllers. */
      use_c_buffer = cinfo->inputctl->has_multiple_scans ||
                     cinfo->buffered_image;
      if (cinfo->data_precision <= 8)
        jinit_d_diff_controller(cinfo, use_c_buffer);
      else if (cinfo->data_precision <= 12)
        j12init_d_diff_controller(cinfo, use_c_buffer);
      else
        j16init_d_diff_controller(cinfo, use_c_buffer);
  #else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
    } else {
      /* Inverse DCT */
      if (cinfo->data_precision == 8)
        jinit_inverse_dct(cinfo);
      else if (cinfo->data_precision == 12)
        j12init_inverse_dct(cinfo);
      else
        ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
      /* Entropy decoding: either Huffman or arithmetic coding. */
      if (cinfo->arith_code) {
  #ifdef D_ARITH_CODING_SUPPORTED
        jinit_arith_decoder(cinfo);
  #else
        ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
  #endif
      } else {
        if (cinfo->progressive_mode) {
  #ifdef D_PROGRESSIVE_SUPPORTED
          jinit_phuff_decoder(cinfo);
  #else
          ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif
        } else
          jinit_huff_decoder(cinfo);
      }
  
      /* Initialize principal buffer controllers. */
      use_c_buffer = cinfo->inputctl->has_multiple_scans ||
                     cinfo->buffered_image;
      if (cinfo->data_precision == 12)
        j12init_d_coef_controller(cinfo, use_c_buffer);
      else
        jinit_d_coef_controller(cinfo, use_c_buffer);
    }
  
    if (!cinfo->raw_data_out) {
      if (cinfo->data_precision <= 8)
        jinit_d_main_controller(cinfo, FALSE /* never need full buffer here */);
      else if (cinfo->data_precision <= 12)
        j12init_d_main_controller(cinfo,
                                  FALSE /* never need full buffer here */);
      else
  #ifdef D_LOSSLESS_SUPPORTED
        j16init_d_main_controller(cinfo,
                                  FALSE /* never need full buffer here */);
  #else
        ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
  #endif
    }
  
    /* We can now tell the memory manager to allocate virtual arrays. */
    (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo);
  
    /* Initialize input side of decompressor to consume first scan. */
    (*cinfo->inputctl->start_input_pass) (cinfo);
  
    /* Set the first and last iMCU columns to decompress from single-scan images.
     * By default, decompress all of the iMCU columns.
     */
    cinfo->master->first_iMCU_col = 0;
    cinfo->master->last_iMCU_col = cinfo->MCUs_per_row - 1;
    cinfo->master->last_good_iMCU_row = 0;
  
  #ifdef D_MULTISCAN_FILES_SUPPORTED
    /* If jpeg_start_decompress will read the whole file, initialize
     * progress monitoring appropriately.  The input step is counted
     * as one pass.
     */
    if (cinfo->progress != NULL && !cinfo->buffered_image &&
        cinfo->inputctl->has_multiple_scans) {
      int nscans;
      /* Estimate number of scans to set pass_limit. */
      if (cinfo->progressive_mode) {
        /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
        nscans = 2 + 3 * cinfo->num_components;
      } else {
        /* For a nonprogressive multiscan file, estimate 1 scan per component. */
        nscans = cinfo->num_components;
      }
      cinfo->progress->pass_counter = 0L;
      cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans;
      cinfo->progress->completed_passes = 0;
      cinfo->progress->total_passes = (cinfo->enable_2pass_quant ? 3 : 2);
      /* Count the input pass as done */
      master->pass_number++;
    }
  #endif /* D_MULTISCAN_FILES_SUPPORTED */
  }
  
  
  /*
   * Per-pass setup.
   * This is called at the beginning of each output pass.  We determine which
   * modules will be active during this pass and give them appropriate
   * start_pass calls.  We also set is_dummy_pass to indicate whether this
   * is a "real" output pass or a dummy pass for color quantization.
   * (In the latter case, jdapistd.c will crank the pass to completion.)
   */
  
  METHODDEF(void)
  prepare_for_output_pass(j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr)cinfo->master;
  
    if (master->pub.is_dummy_pass) {
  #ifdef QUANT_2PASS_SUPPORTED
      /* Final pass of 2-pass quantization */
      master->pub.is_dummy_pass = FALSE;
      (*cinfo->cquantize->start_pass) (cinfo, FALSE);
      (*cinfo->post->start_pass) (cinfo, JBUF_CRANK_DEST);
      (*cinfo->main->start_pass) (cinfo, JBUF_CRANK_DEST);
  #else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
  #endif /* QUANT_2PASS_SUPPORTED */
    } else {
      if (cinfo->quantize_colors && cinfo->colormap == NULL) {
        /* Select new quantization method */
        if (cinfo->two_pass_quantize && cinfo->enable_2pass_quant) {
          cinfo->cquantize = master->quantizer_2pass;
          master->pub.is_dummy_pass = TRUE;
        } else if (cinfo->enable_1pass_quant) {
          cinfo->cquantize = master->quantizer_1pass;
        } else {
          ERREXIT(cinfo, JERR_MODE_CHANGE);
        }
      }
      (*cinfo->idct->start_pass) (cinfo);
      (*cinfo->coef->start_output_pass) (cinfo);
      if (!cinfo->raw_data_out) {
        if (!master->using_merged_upsample)
          (*cinfo->cconvert->start_pass) (cinfo);
        (*cinfo->upsample->start_pass) (cinfo);
        if (cinfo->quantize_colors)
          (*cinfo->cquantize->start_pass) (cinfo, master->pub.is_dummy_pass);
        (*cinfo->post->start_pass) (cinfo,
              (master->pub.is_dummy_pass ? JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
        (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
      }
    }
  
    /* Set up progress monitor's pass info if present */
    if (cinfo->progress != NULL) {
      cinfo->progress->completed_passes = master->pass_number;
      cinfo->progress->total_passes = master->pass_number +
                                      (master->pub.is_dummy_pass ? 2 : 1);
      /* In buffered-image mode, we assume one more output pass if EOI not
       * yet reached, but no more passes if EOI has been reached.
       */
      if (cinfo->buffered_image && !cinfo->inputctl->eoi_reached) {
        cinfo->progress->total_passes += (cinfo->enable_2pass_quant ? 2 : 1);
      }
    }
  }
  
  
  /*
   * Finish up at end of an output pass.
   */
  
  METHODDEF(void)
  finish_output_pass(j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr)cinfo->master;
  
    if (cinfo->quantize_colors)
      (*cinfo->cquantize->finish_pass) (cinfo);
    master->pass_number++;
  }
  
  
  #ifdef D_MULTISCAN_FILES_SUPPORTED
  
  /*
   * Switch to a new external colormap between output passes.
   */
  
  GLOBAL(void)
  jpeg_new_colormap(j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr)cinfo->master;
  
    /* Prevent application from calling me at wrong times */
    if (cinfo->global_state != DSTATE_BUFIMAGE)
      ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  
    if (cinfo->quantize_colors && cinfo->enable_external_quant &&
        cinfo->colormap != NULL) {
      /* Select 2-pass quantizer for external colormap use */
      cinfo->cquantize = master->quantizer_2pass;
      /* Notify quantizer of colormap change */
      (*cinfo->cquantize->new_color_map) (cinfo);
      master->pub.is_dummy_pass = FALSE; /* just in case */
    } else
      ERREXIT(cinfo, JERR_MODE_CHANGE);
  }
  
  #endif /* D_MULTISCAN_FILES_SUPPORTED */
  
  
  /*
   * Initialize master decompression control and select active modules.
   * This is performed at the start of jpeg_start_decompress.
   */
  
  GLOBAL(void)
  jinit_master_decompress(j_decompress_ptr cinfo)
  {
    my_master_ptr master = (my_master_ptr)cinfo->master;
  
    master->pub.prepare_for_output_pass = prepare_for_output_pass;
    master->pub.finish_output_pass = finish_output_pass;
  
    master->pub.is_dummy_pass = FALSE;
    master->pub.jinit_upsampler_no_alloc = FALSE;
  
    master_selection(cinfo);
  }
  

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