jbig2_generic.c.svn-base

来自「SumatraPDF是一款小型开源的pdf阅读工具。虽然玲珑小巧（只有800多K」· SVN-BASE 代码 · 共 637 行 · 第 1/2 页

#ifdef OUTPUT_PBM
  printf("P4\n%d %d\n", GBW, GBH);
#endif

  for (y = 0; y < GBH; y++)
    {
      uint32_t CONTEXT;
      uint32_t line_m1;
      uint32_t line_m2;
      int padded_width = (GBW + 7) & -8;

      line_m1 = (y >= 1) ? gbreg_line[-rowstride] : 0;
      line_m2 = (y >= 2) ? gbreg_line[-(rowstride << 1)] << 4 : 0;
      CONTEXT = ((line_m1 >> 3) & 0x78) | ((line_m1 >> 2) & 0x4) | ((line_m2 >> 3) & 0x380);

      /* 6.2.5.7 3d */
      for (x = 0; x < padded_width; x += 8)
	{
	  byte result = 0;
	  int x_minor;
	  int minor_width = GBW - x > 8 ? 8 : GBW - x;

	  if (y >= 1)
	    line_m1 = (line_m1 << 8) |
	      (x + 8 < GBW ? gbreg_line[-rowstride + (x >> 3) + 1] : 0);

	  if (y >= 2)
	    line_m2 = (line_m2 << 8) |
	      (x + 8 < GBW ? gbreg_line[-(rowstride << 1) + (x >> 3) + 1] << 4: 0);

	  /* This is the speed-critical inner loop. */
	  for (x_minor = 0; x_minor < minor_width; x_minor++)
	    {
	      bool bit;

	      bit = jbig2_arith_decode(as, &GB_stats[CONTEXT]);
	      result |= bit << (7 - x_minor);
	      CONTEXT = ((CONTEXT & 0x1b9) << 1) | bit |
		((line_m1 >> (10 - x_minor)) & 0x8) |
		((line_m1 >> (9 - x_minor)) & 0x4) |
		((line_m2 >> (10 - x_minor)) & 0x80);
	    }
	  gbreg_line[x >> 3] = result;
	}
#ifdef OUTPUT_PBM
      fwrite(gbreg_line, 1, rowstride, stdout);
#endif
      gbreg_line += rowstride;
    }

  return 0;
}

static int
jbig2_decode_generic_template3(Jbig2Ctx *ctx,
			       Jbig2Segment *segment,
			       const Jbig2GenericRegionParams *params,
			       Jbig2ArithState *as,
			       Jbig2Image *image,
			       Jbig2ArithCx *GB_stats)
{
  const int GBW = image->width;
  const int GBH = image->height;
  const int rowstride = image->stride;
  byte *gbreg_line = (byte *)image->data;
  int x, y;

  /* this routine only handles the nominal AT location */

#ifdef OUTPUT_PBM
  printf("P4\n%d %d\n", GBW, GBH);
#endif

  for (y = 0; y < GBH; y++)
    {
      uint32_t CONTEXT;
      uint32_t line_m1;
      int padded_width = (GBW + 7) & -8;

      line_m1 = (y >= 1) ? gbreg_line[-rowstride] : 0;
      CONTEXT = (line_m1 >> 1) & 0x3f0;

      /* 6.2.5.7 3d */
      for (x = 0; x < padded_width; x += 8)
	{
	  byte result = 0;
	  int x_minor;
	  int minor_width = GBW - x > 8 ? 8 : GBW - x;

	  if (y >= 1)
	    line_m1 = (line_m1 << 8) |
	      (x + 8 < GBW ? gbreg_line[-rowstride + (x >> 3) + 1] : 0);

	  /* This is the speed-critical inner loop. */
	  for (x_minor = 0; x_minor < minor_width; x_minor++)
	    {
	      bool bit;

	      bit = jbig2_arith_decode(as, &GB_stats[CONTEXT]);
	      result |= bit << (7 - x_minor);
	      CONTEXT = ((CONTEXT & 0x1f7) << 1) | bit |
		((line_m1 >> (10 - x_minor)) & 0x010);
	    }
	  gbreg_line[x >> 3] = result;
	}
#ifdef OUTPUT_PBM
      fwrite(gbreg_line, 1, rowstride, stdout);
#endif
      gbreg_line += rowstride;
    }

  return 0;
}

static int
jbig2_decode_generic_template3_unopt(Jbig2Ctx *ctx,
                               Jbig2Segment *segment,
                               const Jbig2GenericRegionParams *params,
                               Jbig2ArithState *as,
                               Jbig2Image *image,
                               Jbig2ArithCx *GB_stats)
{
  const int GBW = image->width;
  const int GBH = image->height;
  uint32_t CONTEXT;
  int x,y;
  bool bit;

  /* this version is generic and easy to understand, but very slow */

  for (y = 0; y < GBH; y++) {
    for (x = 0; x < GBW; x++) {
      CONTEXT = 0;
      CONTEXT |= jbig2_image_get_pixel(image, x - 1, y) << 0;
      CONTEXT |= jbig2_image_get_pixel(image, x - 2, y) << 1;
      CONTEXT |= jbig2_image_get_pixel(image, x - 3, y) << 2;
      CONTEXT |= jbig2_image_get_pixel(image, x - 4, y) << 3;
      CONTEXT |= jbig2_image_get_pixel(image, x + params->gbat[0],
	y + params->gbat[1]) << 4;
      CONTEXT |= jbig2_image_get_pixel(image, x + 1, y - 1) << 5;
      CONTEXT |= jbig2_image_get_pixel(image, x + 0, y - 1) << 6;
      CONTEXT |= jbig2_image_get_pixel(image, x - 1, y - 1) << 7;
      CONTEXT |= jbig2_image_get_pixel(image, x - 2, y - 1) << 8;
      CONTEXT |= jbig2_image_get_pixel(image, x - 3, y - 1) << 9;
      bit = jbig2_arith_decode(as, &GB_stats[CONTEXT]);
      jbig2_image_set_pixel(image, x, y, bit);
    }
  }
  return 0;
}


/**
 * jbig2_decode_generic_region: Decode a generic region.
 * @ctx: The context for allocation and error reporting.
 * @segment: A segment reference for error reporting.
 * @params: Decoding parameter set.
 * @as: Arithmetic decoder state.
 * @image: Where to store the decoded data.
 * @GB_stats: Arithmetic stats.
 *
 * Decodes a generic region, according to section 6.2. The caller should
 * pass an already allocated Jbig2Image object for @image
 *
 * Because this API is based on an arithmetic decoding state, it is
 * not suitable for MMR decoding.
 *
 * Return code: 0 on success.
 **/
int
jbig2_decode_generic_region(Jbig2Ctx *ctx,
			    Jbig2Segment *segment,
			    const Jbig2GenericRegionParams *params,
			    Jbig2ArithState *as,
			    Jbig2Image *image,
			    Jbig2ArithCx *GB_stats)
{
  const int8_t *gbat = params->gbat;

  if (!params->MMR && params->GBTEMPLATE == 0) {
    if (gbat[0] == +3 && gbat[1] == -1 &&
        gbat[2] == -3 && gbat[3] == -1 &&
        gbat[4] == +2 && gbat[5] == -2 &&
        gbat[6] == -2 && gbat[7] == -2)
      return jbig2_decode_generic_template0(ctx, segment, params,
                                          as, image, GB_stats);
    else
      return jbig2_decode_generic_template0_unopt(ctx, segment, params,
                                          as, image, GB_stats);
  } else if (!params->MMR && params->GBTEMPLATE == 1)
    return jbig2_decode_generic_template1(ctx, segment, params,
					  as, image, GB_stats);
  else if (!params->MMR && params->GBTEMPLATE == 2)
    {
      if (gbat[0] == 3 && gbat[1] == -1)
	return jbig2_decode_generic_template2a(ctx, segment, params,
					       as, image, GB_stats);
      else
	return jbig2_decode_generic_template2(ctx, segment, params,
                                              as, image, GB_stats);
    }
  else if (!params->MMR && params->GBTEMPLATE == 3) {
   if (gbat[0] == 2 && gbat[1] == -1)
     return jbig2_decode_generic_template3_unopt(ctx, segment, params,
                                         as, image, GB_stats);
   else
     return jbig2_decode_generic_template3_unopt(ctx, segment, params,
                                         as, image, GB_stats);
  }

  {
    int i;
    for (i = 0; i < 8; i++)
      jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, segment->number,
        "gbat[%d] = %d", i, params->gbat[i]);
  }
  jbig2_error(ctx, JBIG2_SEVERITY_WARNING, segment->number,
	      "decode_generic_region: MMR=%d, GBTEMPLATE=%d NYI",
	      params->MMR, params->GBTEMPLATE);
  return -1;
}

/** 
 * Handler for immediate generic region segments
 */
int
jbig2_immediate_generic_region(Jbig2Ctx *ctx, Jbig2Segment *segment,
			       const byte *segment_data)
{
  Jbig2RegionSegmentInfo rsi;
  byte seg_flags;
  int8_t gbat[8];
  int offset;
  int gbat_bytes = 0;
  Jbig2GenericRegionParams params;
  int code;
  Jbig2Image *image;
  Jbig2WordStream *ws;
  Jbig2ArithState *as;
  Jbig2ArithCx *GB_stats = NULL;

  /* 7.4.6 */
  if (segment->data_length < 18)
    return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number,
		       "Segment too short");

  jbig2_get_region_segment_info(&rsi, segment_data);
  jbig2_error(ctx, JBIG2_SEVERITY_INFO, segment->number,
	      "generic region: %d x %d @ (%d, %d), flags = %02x",
	      rsi.width, rsi.height, rsi.x, rsi.y, rsi.flags);

  /* 7.4.6.2 */
  seg_flags = segment_data[17];
  jbig2_error(ctx, JBIG2_SEVERITY_INFO, segment->number,
	      "segment flags = %02x", seg_flags);
  if ((seg_flags & 1) && (seg_flags & 6))
    jbig2_error(ctx, JBIG2_SEVERITY_WARNING, segment->number,
		"MMR is 1, but GBTEMPLATE is not 0");

  /* 7.4.6.3 */
  if (!(seg_flags & 1))
    {
      gbat_bytes = (seg_flags & 6) ? 2 : 8;
      if (18 + gbat_bytes > segment->data_length)
	return jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number,
			   "Segment too short");
      memcpy(gbat, segment_data + 18, gbat_bytes);
      jbig2_error(ctx, JBIG2_SEVERITY_INFO, segment->number,
		  "gbat: %d, %d", gbat[0], gbat[1]);
    }

  offset = 18 + gbat_bytes;

  /* Table 34 */
  params.MMR = seg_flags & 1;
  params.GBTEMPLATE = (seg_flags & 6) >> 1;
  params.TPGDON = (seg_flags & 8) >> 3;
  params.USESKIP = 0;
  memcpy (params.gbat, gbat, gbat_bytes);

  image = jbig2_image_new(ctx, rsi.width, rsi.height);
  jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, segment->number,
    "allocated %d x %d image buffer for region decode results",
        rsi.width, rsi.height);

  if (params.MMR)
    {
      code = jbig2_decode_generic_mmr(ctx, segment, &params,
				      segment_data + offset, segment->data_length - offset,
				      image);
    }
  else
    {
      int stats_size = jbig2_generic_stats_size(ctx, params.GBTEMPLATE);
      GB_stats = jbig2_alloc(ctx->allocator, stats_size);
      memset(GB_stats, 0, stats_size);

      ws = jbig2_word_stream_buf_new(ctx,
				     segment_data + offset,
				     segment->data_length - offset);
      as = jbig2_arith_new(ctx, ws);
      code = jbig2_decode_generic_region(ctx, segment, &params,
					 as, image, GB_stats);
      jbig2_free(ctx->allocator, as);
      jbig2_word_stream_buf_free(ctx, ws);

      jbig2_free(ctx->allocator, GB_stats);
    }

  jbig2_page_add_result(ctx, &ctx->pages[ctx->current_page],
			image, rsi.x, rsi.y, JBIG2_COMPOSE_OR);
  jbig2_image_release(ctx, image);

  return code;
}