jcapistd.c

/* 
 * jcapistd.c 
 * 
 * Copyright (C) 1994-1996, 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.  These are the "standard" API routines that are 
 * used in the normal full-compression case.  They are not used by a 
 * transcoding-only application.  Note that if an application links in 
 * jpeg_start_compress, it will end up linking in the entire compressor. 
 * We thus must separate this file from jcapimin.c to avoid linking the 
 * whole compression library into a transcoder. 
 */ 
 
#define JPEG_INTERNALS 
#include "jinclude.h" 
#include "jpeglib.h" 
 
 
/* 
 * 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 master selection of active modules */ 
  jinit_compress_master(cinfo); 
  /* Set up for the first pass */ 
  (*cinfo->master->prepare_for_pass) (cinfo); 
  /* Ready for application to drive first pass through jpeg_write_scanlines 
   * or jpeg_write_raw_data. 
   */ 
  cinfo->next_scanline = 0; 
  cinfo->global_state = (cinfo->raw_data_in ? CSTATE_RAW_OK : CSTATE_SCANNING); 
} 
 
 
/* 
 * Write some scanlines of data to the JPEG compressor. 
 * 
 * The return value will be the number of lines actually written. 
 * This should be less than the supplied num_lines only in case that 
 * the data destination module has requested suspension of the compressor, 
 * or if more than image_height scanlines are passed in. 
 * 
 * Note: we warn about excess calls to jpeg_write_scanlines() since 
 * this likely signals an application programmer error.  However, 
 * excess scanlines passed in the last valid call are *silently* ignored, 
 * so that the application need not adjust num_lines for end-of-image 
 * when using a multiple-scanline buffer. 
 */ 
 
GLOBAL(JDIMENSION) 
jpeg_write_scanlines (j_compress_ptr cinfo, JSAMPARRAY scanlines, 
		      JDIMENSION num_lines) 
{ 
  JDIMENSION row_ctr, rows_left; 
 
  if (cinfo->global_state != CSTATE_SCANNING) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  if (cinfo->next_scanline >= cinfo->image_height) 
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA); 
 
  /* Call progress monitor hook if present */ 
  if (cinfo->progress != NULL) { 
    cinfo->progress->pass_counter = (long) cinfo->next_scanline; 
    cinfo->progress->pass_limit = (long) cinfo->image_height; 
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 
  } 
 
  /* Give master control module another chance if this is first call to 
   * jpeg_write_scanlines.  This lets output of the frame/scan headers be 
   * delayed so that application can write COM, etc, markers between 
   * jpeg_start_compress and jpeg_write_scanlines. 
   */ 
  if (cinfo->master->call_pass_startup) 
    (*cinfo->master->pass_startup) (cinfo); 
 
  /* Ignore any extra scanlines at bottom of image. */ 
  rows_left = cinfo->image_height - cinfo->next_scanline; 
  if (num_lines > rows_left) 
    num_lines = rows_left; 
 
  row_ctr = 0; 
  (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, num_lines); 
  cinfo->next_scanline += row_ctr; 
  return row_ctr; 
} 
 
 
/* 
 * Alternate entry point to write raw data. 
 * Processes exactly one iMCU row per call, unless suspended. 
 */ 
 
GLOBAL(JDIMENSION) 
jpeg_write_raw_data (j_compress_ptr cinfo, JSAMPIMAGE data, 
		     JDIMENSION num_lines) 
{ 
  JDIMENSION lines_per_iMCU_row; 
 
  if (cinfo->global_state != CSTATE_RAW_OK) 
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state); 
  if (cinfo->next_scanline >= cinfo->image_height) { 
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA); 
    return 0; 
  } 
 
  /* Call progress monitor hook if present */ 
  if (cinfo->progress != NULL) { 
    cinfo->progress->pass_counter = (long) cinfo->next_scanline; 
    cinfo->progress->pass_limit = (long) cinfo->image_height; 
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo); 
  } 
 
  /* Give master control module another chance if this is first call to 
   * jpeg_write_raw_data.  This lets output of the frame/scan headers be 
   * delayed so that application can write COM, etc, markers between 
   * jpeg_start_compress and jpeg_write_raw_data. 
   */ 
  if (cinfo->master->call_pass_startup) 
    (*cinfo->master->pass_startup) (cinfo); 
 
  /* Verify that at least one iMCU row has been passed. */ 
  lines_per_iMCU_row = cinfo->max_v_samp_factor * DCTSIZE; 
  if (num_lines < lines_per_iMCU_row) 
    ERREXIT(cinfo, JERR_BUFFER_SIZE); 
 
  /* Directly compress the row. */ 
  if (! (*cinfo->coef->compress_data) (cinfo, data)) { 
    /* If compressor did not consume the whole row, suspend processing. */ 
    return 0; 
  } 
 
  /* OK, we processed one iMCU row. */ 
  cinfo->next_scanline += lines_per_iMCU_row; 
  return lines_per_iMCU_row; 
}