jcmaster.c

/*
 * jcmaster.c
 *
 * Copyright (C) 1991-1994, 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 selecting the modules to be executed
 * and with 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 struct {
  struct jpeg_comp_master pub;	/* public fields */

  int pass_number;		/* eventually need more complex state... */
} 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++) {
    /* 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));
}


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;
    compptr->last_row_height = 1;
    
    /* 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 > 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);
  }
}


/*
 * Master selection of compression modules.
 * This is done once at the start of processing an image.  We determine
 * which modules will be used and give them appropriate initialization calls.
 */

LOCAL void
master_selection (j_compress_ptr cinfo)
{
  my_master_ptr master = (my_master_ptr) cinfo->master;

  initial_setup(cinfo);
  master->pass_number = 0;

  /* There's not a lot of smarts here right now, but it'll get more
   * complicated when we have multiple implementations available...
   */

  /* Preprocessing */
  if (! cinfo->raw_data_in) {
    jinit_color_converter(cinfo);
    jinit_downsampler(cinfo);
    jinit_c_prep_controller(cinfo, FALSE /* never need full buffer here */);
  }
  /* Forward DCT */
  jinit_forward_dct(cinfo);
  /* Entropy encoding: either Huffman or arithmetic coding. */
  if (cinfo->arith_code) {
#ifdef C_ARITH_CODING_SUPPORTED
    jinit_arith_encoder(cinfo);
#else
    ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
#endif
  } else
    jinit_huff_encoder(cinfo);

  /* For now, a full buffer is needed only for Huffman optimization. */
  jinit_c_coef_controller(cinfo, cinfo->optimize_coding);
  jinit_c_main_controller(cinfo, FALSE /* never need full buffer here */);

  jinit_marker_writer(cinfo);

  /* We can now tell the memory manager to allocate virtual arrays. */
  (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);

  /* Write the datastream header (SOI) immediately.
   * Frame and scan headers are postponed till later.
   * This lets application insert special markers after the SOI.
   */
  (*cinfo->marker->write_file_header) (cinfo);
}


/*
 * 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;
  int ci;
  int npasses;

  /* ???? JUST A QUICK CROCK FOR NOW ??? */

  /* For now, handle only single interleaved output scan; */
  /* we support two passes for Huffman optimization. */

  /* Prepare for single 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];
  }

  per_scan_setup(cinfo);

  if (! cinfo->optimize_coding) {
    /* Standard single-pass case */
    npasses = 1;
    master->pub.call_pass_startup = TRUE;
    master->pub.is_last_pass = TRUE;
    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, FALSE);
    (*cinfo->coef->start_pass) (cinfo, JBUF_PASS_THRU);
    (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
  } else {
    npasses = 2;
    switch (master->pass_number) {
    case 0:
      /* Huffman optimization: run all modules, gather statistics */
      master->pub.call_pass_startup = FALSE;
      master->pub.is_last_pass = FALSE;
      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, TRUE);
      (*cinfo->coef->start_pass) (cinfo, JBUF_SAVE_AND_PASS);
      (*cinfo->main->start_pass) (cinfo, JBUF_PASS_THRU);
      break;
    case 1:
      /* Second pass: reread data from coefficient buffer */
      master->pub.is_last_pass = TRUE;
      (*cinfo->entropy->start_pass) (cinfo, FALSE);
      (*cinfo->coef->start_pass) (cinfo, JBUF_CRANK_DEST);
      /* We emit frame/scan headers now */
      (*cinfo->marker->write_frame_header) (cinfo);
      (*cinfo->marker->write_scan_header) (cinfo);
      break;
    }
  }

  /* Set up progress monitor's pass info if present */
  if (cinfo->progress != NULL) {
    cinfo->progress->completed_passes = master->pass_number;
    cinfo->progress->total_passes = npasses;
  }

  master->pass_number++;
}


/*
 * 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)
{
  /* More complex logic later ??? */

  /* The entropy coder needs an end-of-pass call, either to analyze
   * statistics or to flush its output buffer.
   */
  (*cinfo->entropy->finish_pass) (cinfo);
}


/*
 * Initialize master compression control.
 * This creates my own subrecord and also performs the master selection phase,
 * which causes other modules to create their subrecords.
 */

GLOBAL void
jinit_master_compress (j_compress_ptr cinfo)
{
  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_selection(cinfo);
}