www.pudn.com > imgport.rar > jcmaster.c, change:2008-11-05,size:20479b


/* 
 * jcmaster.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 master control logic for the JPEG compressor. 
 * These routines are concerned with parameter validation, initial setup, 
 * and inter-pass control (determining the number of passes and the work  
 * to be done in each pass). 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
 
/* Private state */ 
 
typedef enum { 
	main_pass,		/* input data, also do first output step */ 
	huff_opt_pass,		/* Huffman code optimization pass */ 
	output_pass		/* data output pass */ 
} c_pass_type; 
 
typedef struct { 
  struct jpeg_comp_master pub;	/* public fields */ 
 
  c_pass_type pass_type;	/* the type of the current pass */ 
 
  int pass_number;		/* # of passes completed */ 
  int total_passes;		/* total # of passes needed */ 
 
  int scan_number;		/* current index in scan_info[] */ 
} my_comp_master; 
 
typedef my_comp_master * my_master_ptr; 
 
 
/* 
 * Support routines that do various essential calculations. 
 */ 
 
LOCAL(void) 
initial_setup (j_compress_ptr cinfo) 
/* Do computations that are needed before master selection phase */ 
{ 
  int ci; 
  jpeg_component_info *compptr; 
  long samplesperrow; 
  JDIMENSION jd_samplesperrow; 
 
  /* Sanity check on image dimensions */ 
  if (cinfo->image_height <= 0 || cinfo->image_width <= 0 
      || cinfo->num_components <= 0 || cinfo->input_components <= 0) 
    ERREXIT(cinfo, JERR_EMPTY_IMAGE); 
 
  /* 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); 
 
  /* Width of an input scanline must be representable as JDIMENSION. */ 
  samplesperrow = (long) cinfo->image_width * (long) cinfo->input_components; 
  jd_samplesperrow = (JDIMENSION) samplesperrow; 
  if ((long) jd_samplesperrow != samplesperrow) 
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW); 
 
  /* 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); 
  } 
 
  /* Compute dimensions of components */ 
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; 
       ci++, compptr++) { 
    /* Fill in the correct component_index value; don't rely on application */ 
    compptr->component_index = ci; 
    /* For compression, we never do DCT scaling. */ 
    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)); 
    /* 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 (this flag isn't actually used for compression) */ 
    compptr->component_needed = TRUE; 
  } 
 
  /* Compute number of fully interleaved MCU rows (number of times that 
   * main controller will call coefficient controller). 
   */ 
  cinfo->total_iMCU_rows = (JDIMENSION) 
    jdiv_round_up((long) cinfo->image_height, 
		  (long) (cinfo->max_v_samp_factor*DCTSIZE)); 
} 
 
 
#ifdef C_MULTISCAN_FILES_SUPPORTED 
 
LOCAL(void) 
validate_script (j_compress_ptr cinfo) 
/* Verify that the scan script in cinfo->scan_info[] is valid; also 
 * determine whether it uses progressive JPEG, and set cinfo->progressive_mode. 
 */ 
{ 
  const jpeg_scan_info * scanptr; 
  int scanno, ncomps, ci, coefi, thisi; 
  int Ss, Se, Ah, Al; 
  boolean component_sent[MAX_COMPONENTS]; 
#ifdef C_PROGRESSIVE_SUPPORTED 
  int * last_bitpos_ptr; 
  int last_bitpos[MAX_COMPONENTS][DCTSIZE2]; 
  /* -1 until that coefficient has been seen; then last Al for it */ 
#endif 
 
  if (cinfo->num_scans <= 0) 
    ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, 0); 
 
  /* For sequential JPEG, all scans must have Ss=0, Se=DCTSIZE2-1; 
   * for progressive JPEG, no scan can have this. 
   */ 
  scanptr = cinfo->scan_info; 
  if (scanptr->Ss != 0 || scanptr->Se != DCTSIZE2-1) { 
#ifdef C_PROGRESSIVE_SUPPORTED 
    cinfo->progressive_mode = TRUE; 
    last_bitpos_ptr = & last_bitpos[0][0]; 
    for (ci = 0; ci < cinfo->num_components; ci++)  
      for (coefi = 0; coefi < DCTSIZE2; coefi++) 
	*last_bitpos_ptr++ = -1; 
#else 
    ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif 
  } else { 
    cinfo->progressive_mode = FALSE; 
    for (ci = 0; ci < cinfo->num_components; ci++)  
      component_sent[ci] = FALSE; 
  } 
 
  for (scanno = 1; scanno <= cinfo->num_scans; scanptr++, scanno++) { 
    /* Validate component indexes */ 
    ncomps = scanptr->comps_in_scan; 
    if (ncomps <= 0 || ncomps > MAX_COMPS_IN_SCAN) 
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, ncomps, MAX_COMPS_IN_SCAN); 
    for (ci = 0; ci < ncomps; ci++) { 
      thisi = scanptr->component_index[ci]; 
      if (thisi < 0 || thisi >= cinfo->num_components) 
	ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno); 
      /* Components must appear in SOF order within each scan */ 
      if (ci > 0 && thisi <= scanptr->component_index[ci-1]) 
	ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno); 
    } 
    /* Validate progression parameters */ 
    Ss = scanptr->Ss; 
    Se = scanptr->Se; 
    Ah = scanptr->Ah; 
    Al = scanptr->Al; 
    if (cinfo->progressive_mode) { 
#ifdef C_PROGRESSIVE_SUPPORTED 
      /* The JPEG spec simply gives the ranges 0..13 for Ah and Al, but that 
       * seems wrong: the upper bound ought to depend on data precision. 
       * Perhaps they really meant 0..N+1 for N-bit precision. 
       * Here we allow 0..10 for 8-bit data; Al larger than 10 results in 
       * out-of-range reconstructed DC values during the first DC scan, 
       * which might cause problems for some decoders. 
       */ 
#if BITS_IN_JSAMPLE == 8 
#define MAX_AH_AL 10 
#else 
#define MAX_AH_AL 13 
#endif 
      if (Ss < 0 || Ss >= DCTSIZE2 || Se < Ss || Se >= DCTSIZE2 || 
	  Ah < 0 || Ah > MAX_AH_AL || Al < 0 || Al > MAX_AH_AL) 
	ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
      if (Ss == 0) { 
	if (Se != 0)		/* DC and AC together not OK */ 
	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
      } else { 
	if (ncomps != 1)	/* AC scans must be for only one component */ 
	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
      } 
      for (ci = 0; ci < ncomps; ci++) { 
	last_bitpos_ptr = & last_bitpos[scanptr->component_index[ci]][0]; 
	if (Ss != 0 && last_bitpos_ptr[0] < 0) /* AC without prior DC scan */ 
	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
	for (coefi = Ss; coefi <= Se; coefi++) { 
	  if (last_bitpos_ptr[coefi] < 0) { 
	    /* first scan of this coefficient */ 
	    if (Ah != 0) 
	      ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
	  } else { 
	    /* not first scan */ 
	    if (Ah != last_bitpos_ptr[coefi] || Al != Ah-1) 
	      ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
	  } 
	  last_bitpos_ptr[coefi] = Al; 
	} 
      } 
#endif 
    } else { 
      /* For sequential JPEG, all progression parameters must be these: */ 
      if (Ss != 0 || Se != DCTSIZE2-1 || Ah != 0 || Al != 0) 
	ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno); 
      /* Make sure components are not sent twice */ 
      for (ci = 0; ci < ncomps; ci++) { 
	thisi = scanptr->component_index[ci]; 
	if (component_sent[thisi]) 
	  ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno); 
	component_sent[thisi] = TRUE; 
      } 
    } 
  } 
 
  /* Now verify that everything got sent. */ 
  if (cinfo->progressive_mode) { 
#ifdef C_PROGRESSIVE_SUPPORTED 
    /* For progressive mode, we only check that at least some DC data 
     * got sent for each component; the spec does not require that all bits 
     * of all coefficients be transmitted.  Would it be wiser to enforce 
     * transmission of all coefficient bits?? 
     */ 
    for (ci = 0; ci < cinfo->num_components; ci++) { 
      if (last_bitpos[ci][0] < 0) 
	ERREXIT(cinfo, JERR_MISSING_DATA); 
    } 
#endif 
  } else { 
    for (ci = 0; ci < cinfo->num_components; ci++) { 
      if (! component_sent[ci]) 
	ERREXIT(cinfo, JERR_MISSING_DATA); 
    } 
  } 
} 
 
#endif /* C_MULTISCAN_FILES_SUPPORTED */ 
 
 
LOCAL(void) 
select_scan_parameters (j_compress_ptr cinfo) 
/* Set up the scan parameters for the current scan */ 
{ 
  int ci; 
 
#ifdef C_MULTISCAN_FILES_SUPPORTED 
  if (cinfo->scan_info != NULL) { 
    /* Prepare for current scan --- the script is already validated */ 
    my_master_ptr master = (my_master_ptr) cinfo->master; 
    const jpeg_scan_info * scanptr = cinfo->scan_info + master->scan_number; 
 
    cinfo->comps_in_scan = scanptr->comps_in_scan; 
    for (ci = 0; ci < scanptr->comps_in_scan; ci++) { 
      cinfo->cur_comp_info[ci] = 
	&cinfo->comp_info[scanptr->component_index[ci]]; 
    } 
    cinfo->Ss = scanptr->Ss; 
    cinfo->Se = scanptr->Se; 
    cinfo->Ah = scanptr->Ah; 
    cinfo->Al = scanptr->Al; 
  } 
  else 
#endif 
  { 
    /* Prepare for single sequential-JPEG scan containing all components */ 
    if (cinfo->num_components > MAX_COMPS_IN_SCAN) 
      ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components, 
	       MAX_COMPS_IN_SCAN); 
    cinfo->comps_in_scan = cinfo->num_components; 
    for (ci = 0; ci < cinfo->num_components; ci++) { 
      cinfo->cur_comp_info[ci] = &cinfo->comp_info[ci]; 
    } 
    cinfo->Ss = 0; 
    cinfo->Se = DCTSIZE2-1; 
    cinfo->Ah = 0; 
    cinfo->Al = 0; 
  } 
} 
 
 
LOCAL(void) 
per_scan_setup (j_compress_ptr cinfo) 
/* Do computations that are needed before processing a JPEG scan */ 
/* cinfo->comps_in_scan and cinfo->cur_comp_info[] are already set */ 
{ 
  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 = DCTSIZE; 
    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 * DCTSIZE; 
      /* 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 > C_MAX_BLOCKS_IN_MCU) 
	ERREXIT(cinfo, JERR_BAD_MCU_SIZE); 
      while (mcublks-- > 0) { 
	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci; 
      } 
    } 
     
  } 
 
  /* Convert restart specified in rows to actual MCU count. */ 
  /* Note that count must fit in 16 bits, so we provide limiting. */ 
  if (cinfo->restart_in_rows > 0) { 
    long nominal = (long) cinfo->restart_in_rows * (long) cinfo->MCUs_per_row; 
    cinfo->restart_interval = (unsigned int) MIN(nominal, 65535L); 
  } 
} 
 
 
/* 
 * Per-pass setup. 
 * This is called at the beginning of each pass.  We determine which modules 
 * will be active during this pass and give them appropriate start_pass calls. 
 * We also set is_last_pass to indicate whether any more passes will be 
 * required. 
 */ 
 
METHODDEF(void) 
prepare_for_pass (j_compress_ptr cinfo) 
{ 
  my_master_ptr master = (my_master_ptr) cinfo->master; 
 
  switch (master->pass_type) { 
  case main_pass: 
    /* Initial pass: will collect input data, and do either Huffman 
     * optimization or data output for the first scan. 
     */ 
    select_scan_parameters(cinfo); 
    per_scan_setup(cinfo); 
    if (! cinfo->raw_data_in) { 
      (*cinfo->cconvert->start_pass) (cinfo); 
      (*cinfo->downsample->start_pass) (cinfo); 
      (*cinfo->prep->start_pass) (cinfo, JBUF_PASS_THRU); 
    } 
    (*cinfo->fdct->start_pass) (cinfo); 
    (*cinfo->entropy->start_pass) (cinfo, cinfo->optimize_coding); 
    (*cinfo->coef->start_pass) (cinfo, 
				(master->total_passes > 1 ? 
				 JBUF_SAVE_AND_PASS : JBUF_PASS_THRU)); 
    (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU); 
    if (cinfo->optimize_coding) { 
      /* No immediate data output; postpone writing frame/scan headers */ 
      master->pub.call_pass_startup = FALSE; 
    } else { 
      /* Will write frame/scan headers at first jpeg_write_scanlines call */ 
      master->pub.call_pass_startup = TRUE; 
    } 
    break; 
#ifdef ENTROPY_OPT_SUPPORTED 
  case huff_opt_pass: 
    /* Do Huffman optimization for a scan after the first one. */ 
    select_scan_parameters(cinfo); 
    per_scan_setup(cinfo); 
    if (cinfo->Ss != 0 || cinfo->Ah == 0 || cinfo->arith_code) { 
      (*cinfo->entropy->start_pass) (cinfo, TRUE); 
      (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST); 
      master->pub.call_pass_startup = FALSE; 
      break; 
    } 
    /* Special case: Huffman DC refinement scans need no Huffman table 
     * and therefore we can skip the optimization pass for them. 
     */ 
    master->pass_type = output_pass; 
    master->pass_number++; 
    /*FALLTHROUGH*/ 
#endif 
  case output_pass: 
    /* Do a data-output pass. */ 
    /* We need not repeat per-scan setup if prior optimization pass did it. */ 
    if (! cinfo->optimize_coding) { 
      select_scan_parameters(cinfo); 
      per_scan_setup(cinfo); 
    } 
    (*cinfo->entropy->start_pass) (cinfo, FALSE); 
    (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST); 
    /* We emit frame/scan headers now */ 
    if (master->scan_number == 0) 
      (*cinfo->marker->write_frame_header) (cinfo); 
    (*cinfo->marker->write_scan_header) (cinfo); 
    master->pub.call_pass_startup = FALSE; 
    break; 
  default: 
    ERREXIT(cinfo, JERR_NOT_COMPILED); 
  } 
 
  master->pub.is_last_pass = (master->pass_number == master->total_passes-1); 
 
  /* 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->total_passes; 
  } 
} 
 
 
/* 
 * Special start-of-pass hook. 
 * This is called by jpeg_write_scanlines if call_pass_startup is TRUE. 
 * In single-pass processing, we need this hook because we don't want to 
 * write frame/scan headers during jpeg_start_compress; we want to let the 
 * application write COM markers etc. between jpeg_start_compress and the 
 * jpeg_write_scanlines loop. 
 * In multi-pass processing, this routine is not used. 
 */ 
 
METHODDEF(void) 
pass_startup (j_compress_ptr cinfo) 
{ 
  cinfo->master->call_pass_startup = FALSE; /* reset flag so call only once */ 
 
  (*cinfo->marker->write_frame_header) (cinfo); 
  (*cinfo->marker->write_scan_header) (cinfo); 
} 
 
 
/* 
 * Finish up at end of pass. 
 */ 
 
METHODDEF(void) 
finish_pass_master (j_compress_ptr cinfo) 
{ 
  my_master_ptr master = (my_master_ptr) cinfo->master; 
 
  /* The entropy coder always needs an end-of-pass call, 
   * either to analyze statistics or to flush its output buffer. 
   */ 
  (*cinfo->entropy->finish_pass) (cinfo); 
 
  /* Update state for next pass */ 
  switch (master->pass_type) { 
  case main_pass: 
    /* next pass is either output of scan 0 (after optimization) 
     * or output of scan 1 (if no optimization). 
     */ 
    master->pass_type = output_pass; 
    if (! cinfo->optimize_coding) 
      master->scan_number++; 
    break; 
  case huff_opt_pass: 
    /* next pass is always output of current scan */ 
    master->pass_type = output_pass; 
    break; 
  case output_pass: 
    /* next pass is either optimization or output of next scan */ 
    if (cinfo->optimize_coding) 
      master->pass_type = huff_opt_pass; 
    master->scan_number++; 
    break; 
  } 
 
  master->pass_number++; 
} 
 
 
/* 
 * Initialize master compression control. 
 */ 
 
GLOBAL(void) 
jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only) 
{ 
  my_master_ptr master; 
 
  master = (my_master_ptr) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, 
				  SIZEOF(my_comp_master)); 
  cinfo->master = (struct jpeg_comp_master *) master; 
  master->pub.prepare_for_pass = prepare_for_pass; 
  master->pub.pass_startup = pass_startup; 
  master->pub.finish_pass = finish_pass_master; 
  master->pub.is_last_pass = FALSE; 
 
  /* Validate parameters, determine derived values */ 
  initial_setup(cinfo); 
 
  if (cinfo->scan_info != NULL) { 
#ifdef C_MULTISCAN_FILES_SUPPORTED 
    validate_script(cinfo); 
#else 
    ERREXIT(cinfo, JERR_NOT_COMPILED); 
#endif 
  } else { 
    cinfo->progressive_mode = FALSE; 
    cinfo->num_scans = 1; 
  } 
 
  if (cinfo->progressive_mode)	/*  TEMPORARY HACK ??? */ 
    cinfo->optimize_coding = TRUE; /* assume default tables no good for progressive mode */ 
 
  /* Initialize my private state */ 
  if (transcode_only) { 
    /* no main pass in transcoding */ 
    if (cinfo->optimize_coding) 
      master->pass_type = huff_opt_pass; 
    else 
      master->pass_type = output_pass; 
  } else { 
    /* for normal compression, first pass is always this type: */ 
    master->pass_type = main_pass; 
  } 
  master->scan_number = 0; 
  master->pass_number = 0; 
  if (cinfo->optimize_coding) 
    master->total_passes = cinfo->num_scans * 2; 
  else 
    master->total_passes = cinfo->num_scans; 
}