src/jpeg/jcapistd.c

   1 /*
   2  * jcapistd.c
   3  *
   4  * Copyright (C) 1994-1996, 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 application interface code for the compression half
   9  * of the JPEG library.  These are the "standard" API routines that are
  10  * used in the normal full-compression case.  They are not used by a
  11  * transcoding-only application.  Note that if an application links in
  12  * jpeg_start_compress, it will end up linking in the entire compressor.
  13  * We thus must separate this file from jcapimin.c to avoid linking the
  14  * whole compression library into a transcoder.
  15  */
  16
  17 #define JPEG_INTERNALS
  18 #include "jinclude.h"
  19 #include "jpeglib.h"
  20
  21
  22 /*
  23  * Compression initialization.
  24  * Before calling this, all parameters and a data destination must be set up.
  25  *
  26  * We require a write_all_tables parameter as a failsafe check when writing
  27  * multiple datastreams from the same compression object.  Since prior runs
  28  * will have left all the tables marked sent_table=TRUE, a subsequent run
  29  * would emit an abbreviated stream (no tables) by default.  This may be what
  30  * is wanted, but for safety's sake it should not be the default behavior:
  31  * programmers should have to make a deliberate choice to emit abbreviated
  32  * images.  Therefore the documentation and examples should encourage people
  33  * to pass write_all_tables=TRUE; then it will take active thought to do the
  34  * wrong thing.
  35  */
  36
  37 GLOBAL(void)
  38 jpeg_start_compress (j_compress_ptr cinfo, boolean write_all_tables)
  39 {
  40   if (cinfo->global_state != CSTATE_START)
  41     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  42
  43   if (write_all_tables)
  44     jpeg_suppress_tables(cinfo, FALSE); /* mark all tables to be written */
  45
  46   /* (Re)initialize error mgr and destination modules */
  47   (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
  48   (*cinfo->dest->init_destination) (cinfo);
  49   /* Perform master selection of active modules */
  50   jinit_compress_master(cinfo);
  51   /* Set up for the first pass */
  52   (*cinfo->master->prepare_for_pass) (cinfo);
  53   /* Ready for application to drive first pass through jpeg_write_scanlines
  54    * or jpeg_write_raw_data.
  55    */
  56   cinfo->next_scanline = 0;
  57   cinfo->global_state = (cinfo->raw_data_in ? CSTATE_RAW_OK : CSTATE_SCANNING);
  58 }
  59
  60
  61 /*
  62  * Write some scanlines of data to the JPEG compressor.
  63  *
  64  * The return value will be the number of lines actually written.
  65  * This should be less than the supplied num_lines only in case that
  66  * the data destination module has requested suspension of the compressor,
  67  * or if more than image_height scanlines are passed in.
  68  *
  69  * Note: we warn about excess calls to jpeg_write_scanlines() since
  70  * this likely signals an application programmer error.  However,
  71  * excess scanlines passed in the last valid call are *silently* ignored,
  72  * so that the application need not adjust num_lines for end-of-image
  73  * when using a multiple-scanline buffer.
  74  */
  75
  76 GLOBAL(JDIMENSION)
  77 jpeg_write_scanlines (j_compress_ptr cinfo, JSAMPARRAY scanlines,
  78                       JDIMENSION num_lines)
  79 {
  80   JDIMENSION row_ctr, rows_left;
  81
  82   if (cinfo->global_state != CSTATE_SCANNING)
  83     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  84   if (cinfo->next_scanline >= cinfo->image_height)
  85     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
  86
  87   /* Call progress monitor hook if present */
  88   if (cinfo->progress != NULL) {
  89     cinfo->progress->pass_counter = (long) cinfo->next_scanline;
  90     cinfo->progress->pass_limit = (long) cinfo->image_height;
  91     (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
  92   }
  93
  94   /* Give master control module another chance if this is first call to
  95    * jpeg_write_scanlines.  This lets output of the frame/scan headers be
  96    * delayed so that application can write COM, etc, markers between
  97    * jpeg_start_compress and jpeg_write_scanlines.
  98    */
  99   if (cinfo->master->call_pass_startup)
 100     (*cinfo->master->pass_startup) (cinfo);
 101
 102   /* Ignore any extra scanlines at bottom of image. */
 103   rows_left = cinfo->image_height - cinfo->next_scanline;
 104   if (num_lines > rows_left)
 105     num_lines = rows_left;
 106
 107   row_ctr = 0;
 108   (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, num_lines);
 109   cinfo->next_scanline += row_ctr;
 110   return row_ctr;
 111 }
 112
 113
 114 /*
 115  * Alternate entry point to write raw data.
 116  * Processes exactly one iMCU row per call, unless suspended.
 117  */
 118
 119 GLOBAL(JDIMENSION)
 120 jpeg_write_raw_data (j_compress_ptr cinfo, JSAMPIMAGE data,
 121                      JDIMENSION num_lines)
 122 {
 123   JDIMENSION lines_per_iMCU_row;
 124
 125   if (cinfo->global_state != CSTATE_RAW_OK)
 126     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
 127   if (cinfo->next_scanline >= cinfo->image_height) {
 128     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
 129     return 0;
 130   }
 131
 132   /* Call progress monitor hook if present */
 133   if (cinfo->progress != NULL) {
 134     cinfo->progress->pass_counter = (long) cinfo->next_scanline;
 135     cinfo->progress->pass_limit = (long) cinfo->image_height;
 136     (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
 137   }
 138
 139   /* Give master control module another chance if this is first call to
 140    * jpeg_write_raw_data.  This lets output of the frame/scan headers be
 141    * delayed so that application can write COM, etc, markers between
 142    * jpeg_start_compress and jpeg_write_raw_data.
 143    */
 144   if (cinfo->master->call_pass_startup)
 145     (*cinfo->master->pass_startup) (cinfo);
 146
 147   /* Verify that at least one iMCU row has been passed. */
 148   lines_per_iMCU_row = cinfo->max_v_samp_factor * DCTSIZE;
 149   if (num_lines < lines_per_iMCU_row)
 150     ERREXIT(cinfo, JERR_BUFFER_SIZE);
 151
 152   /* Directly compress the row. */
 153   if (! (*cinfo->coef->compress_data) (cinfo, data)) {
 154     /* If compressor did not consume the whole row, suspend processing. */
 155     return 0;
 156   }
 157
 158   /* OK, we processed one iMCU row. */
 159   cinfo->next_scanline += lines_per_iMCU_row;
 160   return lines_per_iMCU_row;
 161 }