www.pudn.com > imgport.rar > jdinput.c, change:2008-11-05,size:13928b


/* 
 * jdinput.c 
 * 
 * Copyright (C) 1991-1997, Thomas G. Lane. 
 * This file is part of the Independent JPEG Group's software. 
 * For conditions of distribution and use, see the accompanying README file. 
 * 
 * This file contains input control logic for the JPEG decompressor. 
 * These routines are concerned with controlling the decompressor's input 
 * processing (marker reading and coefficient decoding).  The actual input 
 * reading is done in jdmarker.c, jdhuff.c, and jdphuff.c. 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
/* Private state */ 
 
typedef struct { 
  struct jpeg_input_controller pub; /* public fields */ 
 
  boolean inheaders;		/* TRUE until first SOS is reached */ 
} my_input_controller; 
 
typedef my_input_controller * my_inputctl_ptr; 
 
 
/* Forward declarations */ 
METHODDEF(int) consume_markers JPP((j_decompress_ptr cinfo)); 
 
 
/* 
 * Routines to calculate various quantities related to the size of the image. 
 */ 
 
LOCAL(void) 
initial_setup (j_decompress_ptr cinfo) 
/* Called once, when first SOS marker is reached */ 
{ 
  int ci; 
  jpeg_component_info *compptr; 
 
  /* Make sure image isn't bigger than I can handle */ 
  if ((long) cinfo->image_height > (long) JPEG_MAX_DIMENSION || 
      (long) cinfo->image_width > (long) JPEG_MAX_DIMENSION) 
    ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) JPEG_MAX_DIMENSION); 
 
  /* For now, precision must match compiled-in value... */ 
  if (cinfo->data_precision != BITS_IN_JSAMPLE) 
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision); 
 
  /* Check that number of components won't exceed internal array sizes */ 
  if (cinfo->num_components > MAX_COMPONENTS) 
    ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components, 
	     MAX_COMPONENTS); 
 
  /* Compute maximum sampling factors; check factor validity */ 
  cinfo->max_h_samp_factor = 1; 
  cinfo->max_v_samp_factor = 1; 
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
       ci++, compptr++) { 
    if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR || 
	compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR) 
      ERREXIT(cinfo, JERR_BAD_SAMPLING); 
    cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor, 
				   compptr->h_samp_factor); 
    cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor, 
				   compptr->v_samp_factor); 
  } 
 
  /* We initialize DCT_scaled_size and min_DCT_scaled_size to DCTSIZE. 
   * In the full decompressor, this will be overridden by jdmaster.c; 
   * but in the transcoder, jdmaster.c is not used, so we must do it here. 
   */ 
  cinfo->min_DCT_scaled_size = DCTSIZE; 
 
  /* Compute dimensions of components */ 
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
       ci++, compptr++) { 
    compptr->DCT_scaled_size = DCTSIZE; 
    /* Size in DCT blocks */ 
    compptr->width_in_blocks = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor, 
		    (long) (cinfo->max_h_samp_factor * DCTSIZE)); 
    compptr->height_in_blocks = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor, 
		    (long) (cinfo->max_v_samp_factor * DCTSIZE)); 
    /* downsampled_width and downsampled_height will also be overridden by 
     * jdmaster.c if we are doing full decompression.  The transcoder library 
     * doesn't use these values, but the calling application might. 
     */ 
    /* Size in samples */ 
    compptr->downsampled_width = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor, 
		    (long) cinfo->max_h_samp_factor); 
    compptr->downsampled_height = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor, 
		    (long) cinfo->max_v_samp_factor); 
    /* Mark component needed, until color conversion says otherwise */ 
    compptr->component_needed = TRUE; 
    /* Mark no quantization table yet saved for component */ 
    compptr->quant_table = NULL; 
  } 
 
  /* Compute number of fully interleaved MCU rows. */ 
  cinfo->total_iMCU_rows = (JDIMENSION) 
    jdiv_round_up((long) cinfo->image_height, 
		  (long) (cinfo->max_v_samp_factor*DCTSIZE)); 
 
  /* Decide whether file contains multiple scans */ 
  if (cinfo->comps_in_scan < cinfo->num_components || cinfo->progressive_mode) 
    cinfo->inputctl->has_multiple_scans = TRUE; 
  else 
    cinfo->inputctl->has_multiple_scans = FALSE; 
} 
 
 
LOCAL(void) 
per_scan_setup (j_decompress_ptr cinfo) 
/* Do computations that are needed before processing a JPEG scan */ 
/* cinfo->comps_in_scan and cinfo->cur_comp_info[] were set from SOS marker */ 
{ 
  int ci, mcublks, tmp; 
  jpeg_component_info *compptr; 
 
  if (cinfo->comps_in_scan == 1) { 
 
    /* Noninterleaved (single-component) scan */ 
    compptr = cinfo->cur_comp_info[0]; 
 
    /* Overall image size in MCUs */ 
    cinfo->MCUs_per_row = compptr->width_in_blocks; 
    cinfo->MCU_rows_in_scan = compptr->height_in_blocks; 
 
    /* For noninterleaved scan, always one block per MCU */ 
    compptr->MCU_width = 1; 
    compptr->MCU_height = 1; 
    compptr->MCU_blocks = 1; 
    compptr->MCU_sample_width = compptr->DCT_scaled_size; 
    compptr->last_col_width = 1; 
    /* For noninterleaved scans, it is convenient to define last_row_height 
     * as the number of block rows present in the last iMCU row. 
     */ 
    tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor); 
    if (tmp == 0) tmp = compptr->v_samp_factor; 
    compptr->last_row_height = tmp; 
 
    /* Prepare array describing MCU composition */ 
    cinfo->blocks_in_MCU = 1; 
    cinfo->MCU_membership[0] = 0; 
 
  } else { 
 
    /* Interleaved (multi-component) scan */ 
    if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN) 
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan, 
	       MAX_COMPS_IN_SCAN); 
 
    /* Overall image size in MCUs */ 
    cinfo->MCUs_per_row = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_width, 
		    (long) (cinfo->max_h_samp_factor*DCTSIZE)); 
    cinfo->MCU_rows_in_scan = (JDIMENSION) 
      jdiv_round_up((long) cinfo->image_height, 
		    (long) (cinfo->max_v_samp_factor*DCTSIZE)); 
 
    cinfo->blocks_in_MCU = 0; 
 
    for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 
      compptr = cinfo->cur_comp_info[ci]; 
      /* Sampling factors give # of blocks of component in each MCU */ 
      compptr->MCU_width = compptr->h_samp_factor; 
      compptr->MCU_height = compptr->v_samp_factor; 
      compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height; 
      compptr->MCU_sample_width = compptr->MCU_width * compptr->DCT_scaled_size; 
      /* Figure number of non-dummy blocks in last MCU column & row */ 
      tmp = (int) (compptr->width_in_blocks % compptr->MCU_width); 
      if (tmp == 0) tmp = compptr->MCU_width; 
      compptr->last_col_width = tmp; 
      tmp = (int) (compptr->height_in_blocks % compptr->MCU_height); 
      if (tmp == 0) tmp = compptr->MCU_height; 
      compptr->last_row_height = tmp; 
      /* Prepare array describing MCU composition */ 
      mcublks = compptr->MCU_blocks; 
      if (cinfo->blocks_in_MCU + mcublks > D_MAX_BLOCKS_IN_MCU) 
	ERREXIT(cinfo, JERR_BAD_MCU_SIZE); 
      while (mcublks-- > 0) { 
	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci; 
      } 
    } 
 
  } 
} 
 
 
/* 
 * Save away a copy of the Q-table referenced by each component present 
 * in the current scan, unless already saved during a prior scan. 
 * 
 * In a multiple-scan JPEG file, the encoder could assign different components 
 * the same Q-table slot number, but change table definitions between scans 
 * so that each component uses a different Q-table.  (The IJG encoder is not 
 * currently capable of doing this, but other encoders might.)  Since we want 
 * to be able to dequantize all the components at the end of the file, this 
 * means that we have to save away the table actually used for each component. 
 * We do this by copying the table at the start of the first scan containing 
 * the component. 
 * The JPEG spec prohibits the encoder from changing the contents of a Q-table 
 * slot between scans of a component using that slot.  If the encoder does so 
 * anyway, this decoder will simply use the Q-table values that were current 
 * at the start of the first scan for the component. 
 * 
 * The decompressor output side looks only at the saved quant tables, 
 * not at the current Q-table slots. 
 */ 
 
LOCAL(void) 
latch_quant_tables (j_decompress_ptr cinfo) 
{ 
  int ci, qtblno; 
  jpeg_component_info *compptr; 
  JQUANT_TBL * qtbl; 
 
  for (ci = 0; ci < cinfo->comps_in_scan; ci++) { 
    compptr = cinfo->cur_comp_info[ci]; 
    /* No work if we already saved Q-table for this component */ 
    if (compptr->quant_table != NULL) 
      continue; 
    /* Make sure specified quantization table is present */ 
    qtblno = compptr->quant_tbl_no; 
    if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS || 
	cinfo->quant_tbl_ptrs[qtblno] == NULL) 
      ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno); 
    /* OK, save away the quantization table */ 
    qtbl = (JQUANT_TBL *) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				  SIZEOF(JQUANT_TBL)); 
    MEMCOPY(qtbl, cinfo->quant_tbl_ptrs[qtblno], SIZEOF(JQUANT_TBL)); 
    compptr->quant_table = qtbl; 
  } 
} 
 
 
/* 
 * Initialize the input modules to read a scan of compressed data. 
 * The first call to this is done by jdmaster.c after initializing 
 * the entire decompressor (during jpeg_start_decompress). 
 * Subsequent calls come from consume_markers, below. 
 */ 
 
METHODDEF(void) 
start_input_pass (j_decompress_ptr cinfo) 
{ 
  per_scan_setup(cinfo); 
  latch_quant_tables(cinfo); 
  (*cinfo->entropy->start_pass) (cinfo); 
#if defined(__VISAGECPP__) 
  (*cinfo->coef->start_input_pass2) (cinfo); 
#else 
  (*cinfo->coef->start_input_pass) (cinfo); 
#endif 
  cinfo->inputctl->consume_input = cinfo->coef->consume_data; 
} 
 
 
/* 
 * Finish up after inputting a compressed-data scan. 
 * This is called by the coefficient controller after it's read all 
 * the expected data of the scan. 
 */ 
 
METHODDEF(void) 
finish_input_pass (j_decompress_ptr cinfo) 
{ 
  cinfo->inputctl->consume_input = consume_markers; 
} 
 
 
/* 
 * Read JPEG markers before, between, or after compressed-data scans. 
 * Change state as necessary when a new scan is reached. 
 * Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI. 
 * 
 * The consume_input method pointer points either here or to the 
 * coefficient controller's consume_data routine, depending on whether 
 * we are reading a compressed data segment or inter-segment markers. 
 */ 
 
METHODDEF(int) 
consume_markers (j_decompress_ptr cinfo) 
{ 
  my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl; 
  int val; 
 
  if (inputctl->pub.eoi_reached) /* After hitting EOI, read no further */ 
    return JPEG_REACHED_EOI; 
 
  val = (*cinfo->marker->read_markers) (cinfo); 
 
  switch (val) { 
  case JPEG_REACHED_SOS:	/* Found SOS */ 
    if (inputctl->inheaders) {	/* 1st SOS */ 
      initial_setup(cinfo); 
      inputctl->inheaders = FALSE; 
      /* Note: start_input_pass must be called by jdmaster.c 
       * before any more input can be consumed.  jdapimin.c is 
       * responsible for enforcing this sequencing. 
       */ 
    } else {			/* 2nd or later SOS marker */ 
      if (! inputctl->pub.has_multiple_scans) 
	ERREXIT(cinfo, JERR_EOI_EXPECTED); /* Oops, I wasn't expecting this! */ 
      start_input_pass(cinfo); 
    } 
    break; 
  case JPEG_REACHED_EOI:	/* Found EOI */ 
    inputctl->pub.eoi_reached = TRUE; 
    if (inputctl->inheaders) {	/* Tables-only datastream, apparently */ 
      if (cinfo->marker->saw_SOF) 
	ERREXIT(cinfo, JERR_SOF_NO_SOS); 
    } else { 
      /* Prevent infinite loop in coef ctlr's decompress_data routine 
       * if user set output_scan_number larger than number of scans. 
       */ 
      if (cinfo->output_scan_number > cinfo->input_scan_number) 
	cinfo->output_scan_number = cinfo->input_scan_number; 
    } 
    break; 
  case JPEG_SUSPENDED: 
    break; 
  } 
 
  return val; 
} 
 
 
/* 
 * Reset state to begin a fresh datastream. 
 */ 
 
METHODDEF(void) 
reset_input_controller (j_decompress_ptr cinfo) 
{ 
  my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl; 
 
  inputctl->pub.consume_input = consume_markers; 
  inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */ 
  inputctl->pub.eoi_reached = FALSE; 
  inputctl->inheaders = TRUE; 
  /* Reset other modules */ 
  (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo); 
  (*cinfo->marker->reset_marker_reader) (cinfo); 
  /* Reset progression state -- would be cleaner if entropy decoder did this */ 
  cinfo->coef_bits = NULL; 
} 
 
 
/* 
 * Initialize the input controller module. 
 * This is called only once, when the decompression object is created. 
 */ 
 
GLOBAL(void) 
jinit_input_controller (j_decompress_ptr cinfo) 
{ 
  my_inputctl_ptr inputctl; 
 
  /* Create subobject in permanent pool */ 
  inputctl = (my_inputctl_ptr) 
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, 
				SIZEOF(my_input_controller)); 
  cinfo->inputctl = (struct jpeg_input_controller *) inputctl; 
  /* Initialize method pointers */ 
  inputctl->pub.consume_input = consume_markers; 
  inputctl->pub.reset_input_controller = reset_input_controller; 
  inputctl->pub.start_input_pass = start_input_pass; 
  inputctl->pub.finish_input_pass = finish_input_pass; 
  /* Initialize state: can't use reset_input_controller since we don't 
   * want to try to reset other modules yet. 
   */ 
  inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */ 
  inputctl->pub.eoi_reached = FALSE; 
  inputctl->inheaders = TRUE; 
}