JPEGView/Independent JPEG Group/jcapi.c

/*
 * jcapi.c
 *
 * Copyright (C) 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 application interface code for the compression half of
 * the JPEG library.  Most of the routines intended to be called directly by
 * an application are in this file.  But also see jcparam.c for
 * parameter-setup helper routines, and jcomapi.c for routines shared by
 * compression and decompression.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/*
 * Initialization of a JPEG compression object.
 * The error manager must already be set up (in case memory manager fails).
 */

GLOBAL void
jpeg_create_compress (j_compress_ptr cinfo)
{
  int i;

  /* For debugging purposes, zero the whole master structure.
   * But error manager pointer is already there, so save and restore it.
   */
  {
    struct jpeg_error_mgr * err = cinfo->err;
    MEMZERO(cinfo, SIZEOF(struct jpeg_compress_struct));
    cinfo->err = err;
  }
  cinfo->is_decompressor = FALSE;

  /* 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->dest = NULL;

  cinfo->comp_info = 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;
  }

  cinfo->input_gamma = 1.0;	/* in case application forgets */

  /* OK, I'm ready */
  cinfo->global_state = CSTATE_START;
}


/*
 * Destruction of a JPEG compression object
 */

GLOBAL void
jpeg_destroy_compress (j_compress_ptr cinfo)
{
  jpeg_destroy((j_common_ptr) cinfo); /* use common routine */
}


/*
 * Forcibly suppress or un-suppress all quantization and Huffman tables.
 * Marks all currently defined tables as already written (if suppress)
 * or not written (if !suppress).  This will control whether they get emitted
 * by a subsequent jpeg_start_compress call.
 *
 * This routine is exported for use by applications that want to produce
 * abbreviated JPEG datastreams.  It logically belongs in jcparam.c, but
 * since it is called by jpeg_start_compress, we put it here --- otherwise
 * jcparam.o would be linked whether the application used it or not.
 */

GLOBAL void
jpeg_suppress_tables (j_compress_ptr cinfo, boolean suppress)
{
  int i;
  JQUANT_TBL * qtbl;
  JHUFF_TBL * htbl;

  for (i = 0; i < NUM_QUANT_TBLS; i++) {
    if ((qtbl = cinfo->quant_tbl_ptrs[i]) != NULL)
      qtbl->sent_table = suppress;
  }

  for (i = 0; i < NUM_HUFF_TBLS; i++) {
    if ((htbl = cinfo->dc_huff_tbl_ptrs[i]) != NULL)
      htbl->sent_table = suppress;
    if ((htbl = cinfo->ac_huff_tbl_ptrs[i]) != NULL)
      htbl->sent_table = suppress;
  }
}


/*
 * Compression initialization.
 * Before calling this, all parameters and a data destination must be set up.
 *
 * We require a write_all_tables parameter as a failsafe check when writing
 * multiple datastreams from the same compression object.  Since prior runs
 * will have left all the tables marked sent_table=TRUE, a subsequent run
 * would emit an abbreviated stream (no tables) by default.  This may be what
 * is wanted, but for safety's sake it should not be the default behavior:
 * programmers should have to make a deliberate choice to emit abbreviated
 * images.  Therefore the documentation and examples should encourage people
 * to pass write_all_tables=TRUE; then it will take active thought to do the
 * wrong thing.
 */

GLOBAL void
jpeg_start_compress (j_compress_ptr cinfo, boolean write_all_tables)
{
  if (cinfo->global_state != CSTATE_START)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  if (write_all_tables)
    jpeg_suppress_tables(cinfo, FALSE);	/* mark all tables to be written */

  /* (Re)initialize error mgr and destination modules */
  (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
  (*cinfo->dest->init_destination) (cinfo);
  /* Perform