Home | History | Annotate | Download | only in jpeg-6b
      1 /*
      2  * jcmaster.c
      3  *
      4  * Copyright (C) 1991-1997, Thomas G. Lane.
      5  * This file is part of the Independent JPEG Group's software.
      6  * For conditions of distribution and use, see the accompanying README file.
      7  *
      8  * This file contains master control logic for the JPEG compressor.
      9  * These routines are concerned with parameter validation, initial setup,
     10  * and inter-pass control (determining the number of passes and the work
     11  * to be done in each pass).
     12  */
     13 
     14 #define JPEG_INTERNALS
     15 #include "jinclude.h"
     16 #include "jpeglib.h"
     17 
     18 
     19 /* Private state */
     20 
     21 typedef enum {
     22 	main_pass,		/* input data, also do first output step */
     23 	huff_opt_pass,		/* Huffman code optimization pass */
     24 	output_pass		/* data output pass */
     25 } c_pass_type;
     26 
     27 typedef struct {
     28   struct jpeg_comp_master pub;	/* public fields */
     29 
     30   c_pass_type pass_type;	/* the type of the current pass */
     31 
     32   int pass_number;		/* # of passes completed */
     33   int total_passes;		/* total # of passes needed */
     34 
     35   int scan_number;		/* current index in scan_info[] */
     36 } my_comp_master;
     37 
     38 typedef my_comp_master * my_master_ptr;
     39 
     40 
     41 /*
     42  * Support routines that do various essential calculations.
     43  */
     44 
     45 LOCAL(void)
     46 initial_setup (j_compress_ptr cinfo)
     47 /* Do computations that are needed before master selection phase */
     48 {
     49   int ci;
     50   jpeg_component_info *compptr;
     51   long samplesperrow;
     52   JDIMENSION jd_samplesperrow;
     53 
     54   /* Sanity check on image dimensions */
     55   if (cinfo->image_height <= 0 || cinfo->image_width <= 0
     56       || cinfo->num_components <= 0 || cinfo->input_components <= 0)
     57     ERREXIT(cinfo, JERR_EMPTY_IMAGE);
     58 
     59   /* Make sure image isn't bigger than I can handle */
     60   if ((long) cinfo->image_height > (long) JPEG_MAX_DIMENSION ||
     61       (long) cinfo->image_width > (long) JPEG_MAX_DIMENSION)
     62     ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) JPEG_MAX_DIMENSION);
     63 
     64   /* Width of an input scanline must be representable as JDIMENSION. */
     65   samplesperrow = (long) cinfo->image_width * (long) cinfo->input_components;
     66   jd_samplesperrow = (JDIMENSION) samplesperrow;
     67   if ((long) jd_samplesperrow != samplesperrow)
     68     ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
     69 
     70   /* For now, precision must match compiled-in value... */
     71   if (cinfo->data_precision != BITS_IN_JSAMPLE)
     72     ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
     73 
     74   /* Check that number of components won't exceed internal array sizes */
     75   if (cinfo->num_components > MAX_COMPONENTS)
     76     ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
     77 	     MAX_COMPONENTS);
     78 
     79   /* Compute maximum sampling factors; check factor validity */
     80   cinfo->max_h_samp_factor = 1;
     81   cinfo->max_v_samp_factor = 1;
     82   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     83        ci++, compptr++) {
     84     if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR ||
     85 	compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR)
     86       ERREXIT(cinfo, JERR_BAD_SAMPLING);
     87     cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor,
     88 				   compptr->h_samp_factor);
     89     cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor,
     90 				   compptr->v_samp_factor);
     91   }
     92 
     93   /* Compute dimensions of components */
     94   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
     95        ci++, compptr++) {
     96     /* Fill in the correct component_index value; don't rely on application */
     97     compptr->component_index = ci;
     98     /* For compression, we never do DCT scaling. */
     99     compptr->DCT_scaled_size = DCTSIZE;
    100     /* Size in DCT blocks */
    101     compptr->width_in_blocks = (JDIMENSION)
    102       jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
    103 		    (long) (cinfo->max_h_samp_factor * DCTSIZE));
    104     compptr->height_in_blocks = (JDIMENSION)
    105       jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
    106 		    (long) (cinfo->max_v_samp_factor * DCTSIZE));
    107     /* Size in samples */
    108     compptr->downsampled_width = (JDIMENSION)
    109       jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
    110 		    (long) cinfo->max_h_samp_factor);
    111     compptr->downsampled_height = (JDIMENSION)
    112       jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
    113 		    (long) cinfo->max_v_samp_factor);
    114     /* Mark component needed (this flag isn't actually used for compression) */
    115     compptr->component_needed = TRUE;
    116   }
    117 
    118   /* Compute number of fully interleaved MCU rows (number of times that
    119    * main controller will call coefficient controller).
    120    */
    121   cinfo->total_iMCU_rows = (JDIMENSION)
    122     jdiv_round_up((long) cinfo->image_height,
    123 		  (long) (cinfo->max_v_samp_factor*DCTSIZE));
    124 }
    125 
    126 
    127 #ifdef C_MULTISCAN_FILES_SUPPORTED
    128 
    129 LOCAL(void)
    130 validate_script (j_compress_ptr cinfo)
    131 /* Verify that the scan script in cinfo->scan_info[] is valid; also
    132  * determine whether it uses progressive JPEG, and set cinfo->progressive_mode.
    133  */
    134 {
    135   const jpeg_scan_info * scanptr;
    136   int scanno, ncomps, ci, coefi, thisi;
    137   int Ss, Se, Ah, Al;
    138   boolean component_sent[MAX_COMPONENTS];
    139 #ifdef C_PROGRESSIVE_SUPPORTED
    140   int * last_bitpos_ptr;
    141   int last_bitpos[MAX_COMPONENTS][DCTSIZE2];
    142   /* -1 until that coefficient has been seen; then last Al for it */
    143 #endif
    144 
    145   if (cinfo->num_scans <= 0)
    146     ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, 0);
    147 
    148   /* For sequential JPEG, all scans must have Ss=0, Se=DCTSIZE2-1;
    149    * for progressive JPEG, no scan can have this.
    150    */
    151   scanptr = cinfo->scan_info;
    152   if (scanptr->Ss != 0 || scanptr->Se != DCTSIZE2-1) {
    153 #ifdef C_PROGRESSIVE_SUPPORTED
    154     cinfo->progressive_mode = TRUE;
    155     last_bitpos_ptr = & last_bitpos[0][0];
    156     for (ci = 0; ci < cinfo->num_components; ci++)
    157       for (coefi = 0; coefi < DCTSIZE2; coefi++)
    158 	*last_bitpos_ptr++ = -1;
    159 #else
    160     ERREXIT(cinfo, JERR_NOT_COMPILED);
    161 #endif
    162   } else {
    163     cinfo->progressive_mode = FALSE;
    164     for (ci = 0; ci < cinfo->num_components; ci++)
    165       component_sent[ci] = FALSE;
    166   }
    167 
    168   for (scanno = 1; scanno <= cinfo->num_scans; scanptr++, scanno++) {
    169     /* Validate component indexes */
    170     ncomps = scanptr->comps_in_scan;
    171     if (ncomps <= 0 || ncomps > MAX_COMPS_IN_SCAN)
    172       ERREXIT2(cinfo, JERR_COMPONENT_COUNT, ncomps, MAX_COMPS_IN_SCAN);
    173     for (ci = 0; ci < ncomps; ci++) {
    174       thisi = scanptr->component_index[ci];
    175       if (thisi < 0 || thisi >= cinfo->num_components)
    176 	ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno);
    177       /* Components must appear in SOF order within each scan */
    178       if (ci > 0 && thisi <= scanptr->component_index[ci-1])
    179 	ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno);
    180     }
    181     /* Validate progression parameters */
    182     Ss = scanptr->Ss;
    183     Se = scanptr->Se;
    184     Ah = scanptr->Ah;
    185     Al = scanptr->Al;
    186     if (cinfo->progressive_mode) {
    187 #ifdef C_PROGRESSIVE_SUPPORTED
    188       /* The JPEG spec simply gives the ranges 0..13 for Ah and Al, but that
    189        * seems wrong: the upper bound ought to depend on data precision.
    190        * Perhaps they really meant 0..N+1 for N-bit precision.
    191        * Here we allow 0..10 for 8-bit data; Al larger than 10 results in
    192        * out-of-range reconstructed DC values during the first DC scan,
    193        * which might cause problems for some decoders.
    194        */
    195 #if BITS_IN_JSAMPLE == 8
    196 #define MAX_AH_AL 10
    197 #else
    198 #define MAX_AH_AL 13
    199 #endif
    200       if (Ss < 0 || Ss >= DCTSIZE2 || Se < Ss || Se >= DCTSIZE2 ||
    201 	  Ah < 0 || Ah > MAX_AH_AL || Al < 0 || Al > MAX_AH_AL)
    202 	ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    203       if (Ss == 0) {
    204 	if (Se != 0)		/* DC and AC together not OK */
    205 	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    206       } else {
    207 	if (ncomps != 1)	/* AC scans must be for only one component */
    208 	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    209       }
    210       for (ci = 0; ci < ncomps; ci++) {
    211 	last_bitpos_ptr = & last_bitpos[scanptr->component_index[ci]][0];
    212 	if (Ss != 0 && last_bitpos_ptr[0] < 0) /* AC without prior DC scan */
    213 	  ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    214 	for (coefi = Ss; coefi <= Se; coefi++) {
    215 	  if (last_bitpos_ptr[coefi] < 0) {
    216 	    /* first scan of this coefficient */
    217 	    if (Ah != 0)
    218 	      ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    219 	  } else {
    220 	    /* not first scan */
    221 	    if (Ah != last_bitpos_ptr[coefi] || Al != Ah-1)
    222 	      ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    223 	  }
    224 	  last_bitpos_ptr[coefi] = Al;
    225 	}
    226       }
    227 #endif
    228     } else {
    229       /* For sequential JPEG, all progression parameters must be these: */
    230       if (Ss != 0 || Se != DCTSIZE2-1 || Ah != 0 || Al != 0)
    231 	ERREXIT1(cinfo, JERR_BAD_PROG_SCRIPT, scanno);
    232       /* Make sure components are not sent twice */
    233       for (ci = 0; ci < ncomps; ci++) {
    234 	thisi = scanptr->component_index[ci];
    235 	if (component_sent[thisi])
    236 	  ERREXIT1(cinfo, JERR_BAD_SCAN_SCRIPT, scanno);
    237 	component_sent[thisi] = TRUE;
    238       }
    239     }
    240   }
    241 
    242   /* Now verify that everything got sent. */
    243   if (cinfo->progressive_mode) {
    244 #ifdef C_PROGRESSIVE_SUPPORTED
    245     /* For progressive mode, we only check that at least some DC data
    246      * got sent for each component; the spec does not require that all bits
    247      * of all coefficients be transmitted.  Would it be wiser to enforce
    248      * transmission of all coefficient bits??
    249      */
    250     for (ci = 0; ci < cinfo->num_components; ci++) {
    251       if (last_bitpos[ci][0] < 0)
    252 	ERREXIT(cinfo, JERR_MISSING_DATA);
    253     }
    254 #endif
    255   } else {
    256     for (ci = 0; ci < cinfo->num_components; ci++) {
    257       if (! component_sent[ci])
    258 	ERREXIT(cinfo, JERR_MISSING_DATA);
    259     }
    260   }
    261 }
    262 
    263 #endif /* C_MULTISCAN_FILES_SUPPORTED */
    264 
    265 
    266 LOCAL(void)
    267 select_scan_parameters (j_compress_ptr cinfo)
    268 /* Set up the scan parameters for the current scan */
    269 {
    270   int ci;
    271 
    272 #ifdef C_MULTISCAN_FILES_SUPPORTED
    273   if (cinfo->scan_info != NULL) {
    274     /* Prepare for current scan --- the script is already validated */
    275     my_master_ptr master = (my_master_ptr) cinfo->master;
    276     const jpeg_scan_info * scanptr = cinfo->scan_info + master->scan_number;
    277 
    278     cinfo->comps_in_scan = scanptr->comps_in_scan;
    279     for (ci = 0; ci < scanptr->comps_in_scan; ci++) {
    280       cinfo->cur_comp_info[ci] =
    281 	&cinfo->comp_info[scanptr->component_index[ci]];
    282     }
    283     cinfo->Ss = scanptr->Ss;
    284     cinfo->Se = scanptr->Se;
    285     cinfo->Ah = scanptr->Ah;
    286     cinfo->Al = scanptr->Al;
    287   }
    288   else
    289 #endif
    290   {
    291     /* Prepare for single sequential-JPEG scan containing all components */
    292     if (cinfo->num_components > MAX_COMPS_IN_SCAN)
    293       ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
    294 	       MAX_COMPS_IN_SCAN);
    295     cinfo->comps_in_scan = cinfo->num_components;
    296     for (ci = 0; ci < cinfo->num_components; ci++) {
    297       cinfo->cur_comp_info[ci] = &cinfo->comp_info[ci];
    298     }
    299     cinfo->Ss = 0;
    300     cinfo->Se = DCTSIZE2-1;
    301     cinfo->Ah = 0;
    302     cinfo->Al = 0;
    303   }
    304 }
    305 
    306 
    307 LOCAL(void)
    308 per_scan_setup (j_compress_ptr cinfo)
    309 /* Do computations that are needed before processing a JPEG scan */
    310 /* cinfo->comps_in_scan and cinfo->cur_comp_info[] are already set */
    311 {
    312   int ci, mcublks, tmp;
    313   jpeg_component_info *compptr;
    314 
    315   if (cinfo->comps_in_scan == 1) {
    316 
    317     /* Noninterleaved (single-component) scan */
    318     compptr = cinfo->cur_comp_info[0];
    319 
    320     /* Overall image size in MCUs */
    321     cinfo->MCUs_per_row = compptr->width_in_blocks;
    322     cinfo->MCU_rows_in_scan = compptr->height_in_blocks;
    323 
    324     /* For noninterleaved scan, always one block per MCU */
    325     compptr->MCU_width = 1;
    326     compptr->MCU_height = 1;
    327     compptr->MCU_blocks = 1;
    328     compptr->MCU_sample_width = DCTSIZE;
    329     compptr->last_col_width = 1;
    330     /* For noninterleaved scans, it is convenient to define last_row_height
    331      * as the number of block rows present in the last iMCU row.
    332      */
    333     tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
    334     if (tmp == 0) tmp = compptr->v_samp_factor;
    335     compptr->last_row_height = tmp;
    336 
    337     /* Prepare array describing MCU composition */
    338     cinfo->blocks_in_MCU = 1;
    339     cinfo->MCU_membership[0] = 0;
    340 
    341   } else {
    342 
    343     /* Interleaved (multi-component) scan */
    344     if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
    345       ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
    346 	       MAX_COMPS_IN_SCAN);
    347 
    348     /* Overall image size in MCUs */
    349     cinfo->MCUs_per_row = (JDIMENSION)
    350       jdiv_round_up((long) cinfo->image_width,
    351 		    (long) (cinfo->max_h_samp_factor*DCTSIZE));
    352     cinfo->MCU_rows_in_scan = (JDIMENSION)
    353       jdiv_round_up((long) cinfo->image_height,
    354 		    (long) (cinfo->max_v_samp_factor*DCTSIZE));
    355 
    356     cinfo->blocks_in_MCU = 0;
    357 
    358     for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    359       compptr = cinfo->cur_comp_info[ci];
    360       /* Sampling factors give # of blocks of component in each MCU */
    361       compptr->MCU_width = compptr->h_samp_factor;
    362       compptr->MCU_height = compptr->v_samp_factor;
    363       compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
    364       compptr->MCU_sample_width = compptr->MCU_width * DCTSIZE;
    365       /* Figure number of non-dummy blocks in last MCU column & row */
    366       tmp = (int) (compptr->width_in_blocks % compptr->MCU_width);
    367       if (tmp == 0) tmp = compptr->MCU_width;
    368       compptr->last_col_width = tmp;
    369       tmp = (int) (compptr->height_in_blocks % compptr->MCU_height);
    370       if (tmp == 0) tmp = compptr->MCU_height;
    371       compptr->last_row_height = tmp;
    372       /* Prepare array describing MCU composition */
    373       mcublks = compptr->MCU_blocks;
    374       if (cinfo->blocks_in_MCU + mcublks > C_MAX_BLOCKS_IN_MCU)
    375 	ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
    376       while (mcublks-- > 0) {
    377 	cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
    378       }
    379     }
    380 
    381   }
    382 
    383   /* Convert restart specified in rows to actual MCU count. */
    384   /* Note that count must fit in 16 bits, so we provide limiting. */
    385   if (cinfo->restart_in_rows > 0) {
    386     long nominal = (long) cinfo->restart_in_rows * (long) cinfo->MCUs_per_row;
    387     cinfo->restart_interval = (unsigned int) MIN(nominal, 65535L);
    388   }
    389 }
    390 
    391 
    392 /*
    393  * Per-pass setup.
    394  * This is called at the beginning of each pass.  We determine which modules
    395  * will be active during this pass and give them appropriate start_pass calls.
    396  * We also set is_last_pass to indicate whether any more passes will be
    397  * required.
    398  */
    399 
    400 METHODDEF(void)
    401 prepare_for_pass (j_compress_ptr cinfo)
    402 {
    403   my_master_ptr master = (my_master_ptr) cinfo->master;
    404 
    405   switch (master->pass_type) {
    406   case main_pass:
    407     /* Initial pass: will collect input data, and do either Huffman
    408      * optimization or data output for the first scan.
    409      */
    410     select_scan_parameters(cinfo);
    411     per_scan_setup(cinfo);
    412     if (! cinfo->raw_data_in) {
    413       (*cinfo->cconvert->start_pass) (cinfo);
    414       (*cinfo->downsample->start_pass) (cinfo);
    415       (*cinfo->prep->start_pass) (cinfo, JBUF_PASS_THRU);
    416     }
    417     (*cinfo->fdct->start_pass) (cinfo);
    418     (*cinfo->entropy->start_pass) (cinfo, cinfo->optimize_coding);
    419     (*cinfo->coef->start_pass) (cinfo,
    420 				(master->total_passes > 1 ?
    421 				 JBUF_SAVE_AND_PASS : JBUF_PASS_THRU));
    422     (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
    423     if (cinfo->optimize_coding) {
    424       /* No immediate data output; postpone writing frame/scan headers */
    425       master->pub.call_pass_startup = FALSE;
    426     } else {
    427       /* Will write frame/scan headers at first jpeg_write_scanlines call */
    428       master->pub.call_pass_startup = TRUE;
    429     }
    430     break;
    431 #ifdef ENTROPY_OPT_SUPPORTED
    432   case huff_opt_pass:
    433     /* Do Huffman optimization for a scan after the first one. */
    434     select_scan_parameters(cinfo);
    435     per_scan_setup(cinfo);
    436     if (cinfo->Ss != 0 || cinfo->Ah == 0 || cinfo->arith_code) {
    437       (*cinfo->entropy->start_pass) (cinfo, TRUE);
    438       (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
    439       master->pub.call_pass_startup = FALSE;
    440       break;
    441     }
    442     /* Special case: Huffman DC refinement scans need no Huffman table
    443      * and therefore we can skip the optimization pass for them.
    444      */
    445     master->pass_type = output_pass;
    446     master->pass_number++;
    447     /*FALLTHROUGH*/
    448 #endif
    449   case output_pass:
    450     /* Do a data-output pass. */
    451     /* We need not repeat per-scan setup if prior optimization pass did it. */
    452     if (! cinfo->optimize_coding) {
    453       select_scan_parameters(cinfo);
    454       per_scan_setup(cinfo);
    455     }
    456     (*cinfo->entropy->start_pass) (cinfo, FALSE);
    457     (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
    458     /* We emit frame/scan headers now */
    459     if (master->scan_number == 0)
    460       (*cinfo->marker->write_frame_header) (cinfo);
    461     (*cinfo->marker->write_scan_header) (cinfo);
    462     master->pub.call_pass_startup = FALSE;
    463     break;
    464   default:
    465     ERREXIT(cinfo, JERR_NOT_COMPILED);
    466   }
    467 
    468   master->pub.is_last_pass = (master->pass_number == master->total_passes-1);
    469 
    470   /* Set up progress monitor's pass info if present */
    471   if (cinfo->progress != NULL) {
    472     cinfo->progress->completed_passes = master->pass_number;
    473     cinfo->progress->total_passes = master->total_passes;
    474   }
    475 }
    476 
    477 
    478 /*
    479  * Special start-of-pass hook.
    480  * This is called by jpeg_write_scanlines if call_pass_startup is TRUE.
    481  * In single-pass processing, we need this hook because we don't want to
    482  * write frame/scan headers during jpeg_start_compress; we want to let the
    483  * application write COM markers etc. between jpeg_start_compress and the
    484  * jpeg_write_scanlines loop.
    485  * In multi-pass processing, this routine is not used.
    486  */
    487 
    488 METHODDEF(void)
    489 pass_startup (j_compress_ptr cinfo)
    490 {
    491   cinfo->master->call_pass_startup = FALSE; /* reset flag so call only once */
    492 
    493   (*cinfo->marker->write_frame_header) (cinfo);
    494   (*cinfo->marker->write_scan_header) (cinfo);
    495 }
    496 
    497 
    498 /*
    499  * Finish up at end of pass.
    500  */
    501 
    502 METHODDEF(void)
    503 finish_pass_master (j_compress_ptr cinfo)
    504 {
    505   my_master_ptr master = (my_master_ptr) cinfo->master;
    506 
    507   /* The entropy coder always needs an end-of-pass call,
    508    * either to analyze statistics or to flush its output buffer.
    509    */
    510   (*cinfo->entropy->finish_pass) (cinfo);
    511 
    512   /* Update state for next pass */
    513   switch (master->pass_type) {
    514   case main_pass:
    515     /* next pass is either output of scan 0 (after optimization)
    516      * or output of scan 1 (if no optimization).
    517      */
    518     master->pass_type = output_pass;
    519     if (! cinfo->optimize_coding)
    520       master->scan_number++;
    521     break;
    522   case huff_opt_pass:
    523     /* next pass is always output of current scan */
    524     master->pass_type = output_pass;
    525     break;
    526   case output_pass:
    527     /* next pass is either optimization or output of next scan */
    528     if (cinfo->optimize_coding)
    529       master->pass_type = huff_opt_pass;
    530     master->scan_number++;
    531     break;
    532   }
    533 
    534   master->pass_number++;
    535 }
    536 
    537 
    538 /*
    539  * Initialize master compression control.
    540  */
    541 
    542 GLOBAL(void)
    543 jinit_c_master_control (j_compress_ptr cinfo, boolean transcode_only)
    544 {
    545   my_master_ptr master;
    546 
    547   master = (my_master_ptr)
    548       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    549 				  SIZEOF(my_comp_master));
    550   cinfo->master = (struct jpeg_comp_master *) master;
    551   master->pub.prepare_for_pass = prepare_for_pass;
    552   master->pub.pass_startup = pass_startup;
    553   master->pub.finish_pass = finish_pass_master;
    554   master->pub.is_last_pass = FALSE;
    555 
    556   /* Validate parameters, determine derived values */
    557   initial_setup(cinfo);
    558 
    559   if (cinfo->scan_info != NULL) {
    560 #ifdef C_MULTISCAN_FILES_SUPPORTED
    561     validate_script(cinfo);
    562 #else
    563     ERREXIT(cinfo, JERR_NOT_COMPILED);
    564 #endif
    565   } else {
    566     cinfo->progressive_mode = FALSE;
    567     cinfo->num_scans = 1;
    568   }
    569 
    570   if (cinfo->progressive_mode)	/*  TEMPORARY HACK ??? */
    571     cinfo->optimize_coding = TRUE; /* assume default tables no good for progressive mode */
    572 
    573   /* Initialize my private state */
    574   if (transcode_only) {
    575     /* no main pass in transcoding */
    576     if (cinfo->optimize_coding)
    577       master->pass_type = huff_opt_pass;
    578     else
    579       master->pass_type = output_pass;
    580   } else {
    581     /* for normal compression, first pass is always this type: */
    582     master->pass_type = main_pass;
    583   }
    584   master->scan_number = 0;
    585   master->pass_number = 0;
    586   if (cinfo->optimize_coding)
    587     master->total_passes = cinfo->num_scans * 2;
    588   else
    589     master->total_passes = cinfo->num_scans;
    590 }
    591