www.pudn.com > imgport.rar > jdapimin.c, change:2008-11-05,size:13032b


/* 
 * jdapimin.c 
 * 
 * Copyright (C) 1994-1998, 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 application interface code for the decompression half 
 * of the JPEG library.  These are the "minimum" API routines that may be 
 * needed in either the normal full-decompression case or the 
 * transcoding-only case. 
 * 
 * Most of the routines intended to be called directly by an application 
 * are in this file or in jdapistd.c.  But also see jcomapi.c for routines 
 * shared by compression and decompression, and jdtrans.c for the transcoding 
 * case. 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
 
/* 
 * Initialization of a JPEG decompression object. 
 * The error manager must already be set up (in case memory manager fails). 
 */ 
 
GLOBAL(void) 
jpeg_CreateDecompress (j_decompress_ptr cinfo, int version, size_t structsize) 
{ 
  int i; 
 
  /* Guard against version mismatches between library and caller. */ 
  cinfo->mem = NULL;		/* so jpeg_destroy knows mem mgr not called */ 
  if (version != JPEG_LIB_VERSION) 
    ERREXIT2(cinfo, JERR_BAD_LIB_VERSION, JPEG_LIB_VERSION, version); 
  if (structsize != SIZEOF(struct jpeg_decompress_struct)) 
    ERREXIT2(cinfo, JERR_BAD_STRUCT_SIZE,  
	     (int) SIZEOF(struct jpeg_decompress_struct), (int) structsize); 
 
  /* For debugging purposes, we zero the whole master structure. 
   * But the application has already set the err pointer, and may have set 
   * client_data, so we have to save and restore those fields. 
   * Note: if application hasn't set client_data, tools like Purify may 
   * complain here. 
   */ 
  { 
    struct jpeg_error_mgr * err = cinfo->err; 
    void * client_data = cinfo->client_data; /* ignore Purify complaint here */ 
    MEMZERO(cinfo, SIZEOF(struct jpeg_decompress_struct)); 
    cinfo->err = err; 
    cinfo->client_data = client_data; 
  } 
  cinfo->is_decompressor = TRUE; 
 
  /* Initialize a memory manager instance for this object */ 
  jinit_memory_mgr((j_common_ptr) cinfo); 
 
  /* Zero out pointers to permanent structures. */ 
  cinfo->progress = NULL; 
  cinfo->src = NULL; 
 
  for (i = 0; i < NUM_QUANT_TBLS; i++) 
    cinfo->quant_tbl_ptrs[i] = NULL; 
 
  for (i = 0; i < NUM_HUFF_TBLS; i++) { 
    cinfo->dc_huff_tbl_ptrs[i] = NULL; 
    cinfo->ac_huff_tbl_ptrs[i] = NULL; 
  } 
 
  /* Initialize marker processor so application can override methods 
   * for COM, APPn markers before calling jpeg_read_header. 
   */ 
  cinfo->marker_list = NULL; 
  jinit_marker_reader(cinfo); 
 
  /* And initialize the overall input controller. */ 
  jinit_input_controller(cinfo); 
 
  /* OK, I'm ready */ 
  cinfo->global_state = DSTATE_START; 
} 
 
 
/* 
 * Destruction of a JPEG decompression object 
 */ 
 
GLOBAL(void) 
jpeg_destroy_decompress (j_decompress_ptr cinfo) 
{ 
  jpeg_destroy((j_common_ptr) cinfo); /* use common routine */ 
} 
 
 
/* 
 * Abort processing of a JPEG decompression operation, 
 * but don't destroy the object itself. 
 */ 
 
GLOBAL(void) 
jpeg_abort_decompress (j_decompress_ptr cinfo) 
{ 
  jpeg_abort((j_common_ptr) cinfo); /* use common routine */ 
} 
 
 
/* 
 * Set default decompression parameters. 
 */ 
 
LOCAL(void) 
default_decompress_parms (j_decompress_ptr cinfo) 
{ 
  /* Guess the input colorspace, and set output colorspace accordingly. */ 
  /* (Wish JPEG committee had provided a real way to specify this...) */ 
  /* Note application may override our guesses. */ 
  switch (cinfo->num_components) { 
  case 1: 
    cinfo->jpeg_color_space = JCS_GRAYSCALE; 
    cinfo->out_color_space = JCS_GRAYSCALE; 
    break; 
     
  case 3: 
    if (cinfo->saw_JFIF_marker) { 
      cinfo->jpeg_color_space = JCS_YCbCr; /* JFIF implies YCbCr */ 
    } else if (cinfo->saw_Adobe_marker) { 
      switch (cinfo->Adobe_transform) { 
      case 0: 
	cinfo->jpeg_color_space = JCS_RGB; 
	break; 
      case 1: 
	cinfo->jpeg_color_space = JCS_YCbCr; 
	break; 
      default: 
	WARNMS1(cinfo, JWRN_ADOBE_XFORM, cinfo->Adobe_transform); 
	cinfo->jpeg_color_space = JCS_YCbCr; /* assume it's YCbCr */ 
	break; 
      } 
    } else { 
      /* Saw no special markers, try to guess from the component IDs */ 
      int cid0 = cinfo->comp_info[0].component_id; 
      int cid1 = cinfo->comp_info[1].component_id; 
      int cid2 = cinfo->comp_info[2].component_id; 
 
      if (cid0 == 1 && cid1 == 2 && cid2 == 3) 
	cinfo->jpeg_color_space = JCS_YCbCr; /* assume JFIF w/out marker */ 
      else if (cid0 == 82 && cid1 == 71 && cid2 == 66) 
	cinfo->jpeg_color_space = JCS_RGB; /* ASCII 'R', 'G', 'B' */ 
      else { 
	TRACEMS3(cinfo, 1, JTRC_UNKNOWN_IDS, cid0, cid1, cid2); 
	cinfo->jpeg_color_space = JCS_YCbCr; /* assume it's YCbCr */ 
      } 
    } 
    /* Always guess RGB is proper output colorspace. */ 
    cinfo->out_color_space = JCS_RGB; 
    break; 
     
  case 4: 
    if (cinfo->saw_Adobe_marker) { 
      switch (cinfo->Adobe_transform) { 
      case 0: 
	cinfo->jpeg_color_space = JCS_CMYK; 
	break; 
      case 2: 
	cinfo->jpeg_color_space = JCS_YCCK; 
	break; 
      default: 
	WARNMS1(cinfo, JWRN_ADOBE_XFORM, cinfo->Adobe_transform); 
	cinfo->jpeg_color_space = JCS_YCCK; /* assume it's YCCK */ 
	break; 
      } 
    } else { 
      /* No special markers, assume straight CMYK. */ 
      cinfo->jpeg_color_space = JCS_CMYK; 
    } 
    cinfo->out_color_space = JCS_CMYK; 
    break; 
     
  default: 
    cinfo->jpeg_color_space = JCS_UNKNOWN; 
    cinfo->out_color_space = JCS_UNKNOWN; 
    break; 
  } 
 
  /* Set defaults for other decompression parameters. */ 
  cinfo->scale_num = 1;		/* 1:1 scaling */ 
  cinfo->scale_denom = 1; 
  cinfo->output_gamma = 1.0; 
  cinfo->buffered_image = FALSE; 
  cinfo->raw_data_out = FALSE; 
  cinfo->dct_method = JDCT_DEFAULT; 
  cinfo->do_fancy_upsampling = TRUE; 
  cinfo->do_block_smoothing = TRUE; 
  cinfo->quantize_colors = FALSE; 
  /* We set these in case application only sets quantize_colors. */ 
  cinfo->dither_mode = JDITHER_FS; 
#ifdef QUANT_2PASS_SUPPORTED 
  cinfo->two_pass_quantize = TRUE; 
#else 
  cinfo->two_pass_quantize = FALSE; 
#endif 
  cinfo->desired_number_of_colors = 256; 
  cinfo->colormap = NULL; 
  /* Initialize for no mode change in buffered-image mode. */ 
  cinfo->enable_1pass_quant = FALSE; 
  cinfo->enable_external_quant = FALSE; 
  cinfo->enable_2pass_quant = FALSE; 
} 
 
 
/* 
 * Decompression startup: read start of JPEG datastream to see what's there. 
 * Need only initialize JPEG object and supply a data source before calling. 
 * 
 * This routine will read as far as the first SOS marker (ie, actual start of 
 * compressed data), and will save all tables and parameters in the JPEG 
 * object.  It will also initialize the decompression parameters to default 
 * values, and finally return JPEG_HEADER_OK.  On return, the application may 
 * adjust the decompression parameters and then call jpeg_start_decompress. 
 * (Or, if the application only wanted to determine the image parameters, 
 * the data need not be decompressed.  In that case, call jpeg_abort or 
 * jpeg_destroy to release any temporary space.) 
 * If an abbreviated (tables only) datastream is presented, the routine will 
 * return JPEG_HEADER_TABLES_ONLY upon reaching EOI.  The application may then 
 * re-use the JPEG object to read the abbreviated image datastream(s). 
 * It is unnecessary (but OK) to call jpeg_abort in this case. 
 * The JPEG_SUSPENDED return code only occurs if the data source module 
 * requests suspension of the decompressor.  In this case the application 
 * should load more source data and then re-call jpeg_read_header to resume 
 * processing. 
 * If a non-suspending data source is used and require_image is TRUE, then the 
 * return code need not be inspected since only JPEG_HEADER_OK is possible. 
 * 
 * This routine is now just a front end to jpeg_consume_input, with some 
 * extra error checking. 
 */ 
 
GLOBAL(int) 
jpeg_read_header (j_decompress_ptr cinfo, boolean require_image) 
{ 
  int retcode; 
 
  if (cinfo->global_state != DSTATE_START && 
      cinfo->global_state != DSTATE_INHEADER) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
 
  retcode = jpeg_consume_input(cinfo); 
 
  switch (retcode) { 
  case JPEG_REACHED_SOS: 
    retcode = JPEG_HEADER_OK; 
    break; 
  case JPEG_REACHED_EOI: 
    if (require_image)		/* Complain if application wanted an image */ 
      ERREXIT(cinfo, JERR_NO_IMAGE); 
    /* Reset to start state; it would be safer to require the application to 
     * call jpeg_abort, but we can't change it now for compatibility reasons. 
     * A side effect is to free any temporary memory (there shouldn't be any). 
     */ 
    jpeg_abort((j_common_ptr) cinfo); /* sets state = DSTATE_START */ 
    retcode = JPEG_HEADER_TABLES_ONLY; 
    break; 
  case JPEG_SUSPENDED: 
    /* no work */ 
    break; 
  } 
 
  return retcode; 
} 
 
 
/* 
 * Consume data in advance of what the decompressor requires. 
 * This can be called at any time once the decompressor object has 
 * been created and a data source has been set up. 
 * 
 * This routine is essentially a state machine that handles a couple 
 * of critical state-transition actions, namely initial setup and 
 * transition from header scanning to ready-for-start_decompress. 
 * All the actual input is done via the input controller's consume_input 
 * method. 
 */ 
 
GLOBAL(int) 
jpeg_consume_input (j_decompress_ptr cinfo) 
{ 
  int retcode = JPEG_SUSPENDED; 
 
  /* NB: every possible DSTATE value should be listed in this switch */ 
  switch (cinfo->global_state) { 
  case DSTATE_START: 
    /* Start-of-datastream actions: reset appropriate modules */ 
    (*cinfo->inputctl->reset_input_controller) (cinfo); 
    /* Initialize application's data source module */ 
    (*cinfo->src->init_source) (cinfo); 
    cinfo->global_state = DSTATE_INHEADER; 
    /*FALLTHROUGH*/ 
  case DSTATE_INHEADER: 
    retcode = (*cinfo->inputctl->consume_input) (cinfo); 
    if (retcode == JPEG_REACHED_SOS) { /* Found SOS, prepare to decompress */ 
      /* Set up default parameters based on header data */ 
      default_decompress_parms(cinfo); 
      /* Set global state: ready for start_decompress */ 
      cinfo->global_state = DSTATE_READY; 
    } 
    break; 
  case DSTATE_READY: 
    /* Can't advance past first SOS until start_decompress is called */ 
    retcode = JPEG_REACHED_SOS; 
    break; 
  case DSTATE_PRELOAD: 
  case DSTATE_PRESCAN: 
  case DSTATE_SCANNING: 
  case DSTATE_RAW_OK: 
  case DSTATE_BUFIMAGE: 
  case DSTATE_BUFPOST: 
  case DSTATE_STOPPING: 
    retcode = (*cinfo->inputctl->consume_input) (cinfo); 
    break; 
  default: 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  } 
  return retcode; 
} 
 
 
/* 
 * Have we finished reading the input file? 
 */ 
 
GLOBAL(boolean) 
jpeg_input_complete (j_decompress_ptr cinfo) 
{ 
  /* Check for valid jpeg object */ 
  if (cinfo->global_state < DSTATE_START || 
      cinfo->global_state > DSTATE_STOPPING) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  return cinfo->inputctl->eoi_reached; 
} 
 
 
/* 
 * Is there more than one scan? 
 */ 
 
GLOBAL(boolean) 
jpeg_has_multiple_scans (j_decompress_ptr cinfo) 
{ 
  /* Only valid after jpeg_read_header completes */ 
  if (cinfo->global_state < DSTATE_READY || 
      cinfo->global_state > DSTATE_STOPPING) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  return cinfo->inputctl->has_multiple_scans; 
} 
 
 
/* 
 * Finish JPEG decompression. 
 * 
 * This will normally just verify the file trailer and release temp storage. 
 * 
 * Returns FALSE if suspended.  The return value need be inspected only if 
 * a suspending data source is used. 
 */ 
 
GLOBAL(boolean) 
jpeg_finish_decompress (j_decompress_ptr cinfo) 
{ 
  if ((cinfo->global_state == DSTATE_SCANNING || 
       cinfo->global_state == DSTATE_RAW_OK) && ! cinfo->buffered_image) { 
    /* Terminate final pass of non-buffered mode */ 
    if (cinfo->output_scanline < cinfo->output_height) 
      ERREXIT(cinfo, JERR_TOO_LITTLE_DATA); 
    (*cinfo->master->finish_output_pass) (cinfo); 
    cinfo->global_state = DSTATE_STOPPING; 
  } else if (cinfo->global_state == DSTATE_BUFIMAGE) { 
    /* Finishing after a buffered-image operation */ 
    cinfo->global_state = DSTATE_STOPPING; 
  } else if (cinfo->global_state != DSTATE_STOPPING) { 
    /* STOPPING = repeat call after a suspension, anything else is error */ 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  } 
  /* Read until EOI */ 
  while (! cinfo->inputctl->eoi_reached) { 
    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED) 
      return FALSE;		/* Suspend, come back later */ 
  } 
  /* Do final cleanup */ 
  (*cinfo->src->term_source) (cinfo); 
  /* We can use jpeg_abort to release memory and reset global_state */ 
  jpeg_abort((j_common_ptr) cinfo); 
  return TRUE; 
}