jcapistd.c

00001 /*
00002  * jcapistd.c
00003  *
00004  * Copyright (C) 1994-1996, Thomas G. Lane.
00005  * Modified 2013 by Guido Vollbeding.
00006  * This file is part of the Independent JPEG Group's software.
00007  * For conditions of distribution and use, see the accompanying README file.
00008  *
00009  * This file contains application interface code for the compression half
00010  * of the JPEG library.  These are the "standard" API routines that are
00011  * used in the normal full-compression case.  They are not used by a
00012  * transcoding-only application.  Note that if an application links in
00013  * jpeg_start_compress, it will end up linking in the entire compressor.
00014  * We thus must separate this file from jcapimin.c to avoid linking the
00015  * whole compression library into a transcoder.
00016  */
00017 
00018 #define JPEG_INTERNALS
00019 #include "jinclude.h"
00020 #include "jpeglib.h"
00021 
00022 
00023 /*
00024  * Compression initialization.
00025  * Before calling this, all parameters and a data destination must be set up.
00026  *
00027  * We require a write_all_tables parameter as a failsafe check when writing
00028  * multiple datastreams from the same compression object.  Since prior runs
00029  * will have left all the tables marked sent_table=TRUE, a subsequent run
00030  * would emit an abbreviated stream (no tables) by default.  This may be what
00031  * is wanted, but for safety's sake it should not be the default behavior:
00032  * programmers should have to make a deliberate choice to emit abbreviated
00033  * images.  Therefore the documentation and examples should encourage people
00034  * to pass write_all_tables=TRUE; then it will take active thought to do the
00035  * wrong thing.
00036  */
00037 
00038 GLOBAL(void)
00039 jpeg_start_compress (j_compress_ptr cinfo, boolean write_all_tables)
00040 {
00041   if (cinfo->global_state != CSTATE_START)
00042     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
00043 
00044   if (write_all_tables)
00045     jpeg_suppress_tables(cinfo, FALSE); /* mark all tables to be written */
00046 
00047   /* (Re)initialize error mgr and destination modules */
00048   (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
00049   (*cinfo->dest->init_destination) (cinfo);
00050   /* Perform master selection of active modules */
00051   jinit_compress_master(cinfo);
00052   /* Set up for the first pass */
00053   (*cinfo->master->prepare_for_pass) (cinfo);
00054   /* Ready for application to drive first pass through jpeg_write_scanlines
00055    * or jpeg_write_raw_data.
00056    */
00057   cinfo->next_scanline = 0;
00058   cinfo->global_state = (cinfo->raw_data_in ? CSTATE_RAW_OK : CSTATE_SCANNING);
00059 }
00060 
00061 
00062 /*
00063  * Write some scanlines of data to the JPEG compressor.
00064  *
00065  * The return value will be the number of lines actually written.
00066  * This should be less than the supplied num_lines only in case that
00067  * the data destination module has requested suspension of the compressor,
00068  * or if more than image_height scanlines are passed in.
00069  *
00070  * Note: we warn about excess calls to jpeg_write_scanlines() since
00071  * this likely signals an application programmer error.  However,
00072  * excess scanlines passed in the last valid call are *silently* ignored,
00073  * so that the application need not adjust num_lines for end-of-image
00074  * when using a multiple-scanline buffer.
00075  */
00076 
00077 GLOBAL(JDIMENSION)
00078 jpeg_write_scanlines (j_compress_ptr cinfo, JSAMPARRAY scanlines,
00079               JDIMENSION num_lines)
00080 {
00081   JDIMENSION row_ctr, rows_left;
00082 
00083   if (cinfo->global_state != CSTATE_SCANNING)
00084     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
00085   if (cinfo->next_scanline >= cinfo->image_height)
00086     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
00087 
00088   /* Call progress monitor hook if present */
00089   if (cinfo->progress != NULL) {
00090     cinfo->progress->pass_counter = (long) cinfo->next_scanline;
00091     cinfo->progress->pass_limit = (long) cinfo->image_height;
00092     (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
00093   }
00094 
00095   /* Give master control module another chance if this is first call to
00096    * jpeg_write_scanlines.  This lets output of the frame/scan headers be
00097    * delayed so that application can write COM, etc, markers between
00098    * jpeg_start_compress and jpeg_write_scanlines.
00099    */
00100   if (cinfo->master->call_pass_startup)
00101     (*cinfo->master->pass_startup) (cinfo);
00102 
00103   /* Ignore any extra scanlines at bottom of image. */
00104   rows_left = cinfo->image_height - cinfo->next_scanline;
00105   if (num_lines > rows_left)
00106     num_lines = rows_left;
00107 
00108   row_ctr = 0;
00109   (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, num_lines);
00110   cinfo->next_scanline += row_ctr;
00111   return row_ctr;
00112 }
00113 
00114 
00115 /*
00116  * Alternate entry point to write raw data.
00117  * Processes exactly one iMCU row per call, unless suspended.
00118  */
00119 
00120 GLOBAL(JDIMENSION)
00121 jpeg_write_raw_data (j_compress_ptr cinfo, JSAMPIMAGE data,
00122              JDIMENSION num_lines)
00123 {
00124   JDIMENSION lines_per_iMCU_row;
00125 
00126   if (cinfo->global_state != CSTATE_RAW_OK)
00127     ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
00128   if (cinfo->next_scanline >= cinfo->image_height) {
00129     WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
00130     return 0;
00131   }
00132 
00133   /* Call progress monitor hook if present */
00134   if (cinfo->progress != NULL) {
00135     cinfo->progress->pass_counter = (long) cinfo->next_scanline;
00136     cinfo->progress->pass_limit = (long) cinfo->image_height;
00137     (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
00138   }
00139 
00140   /* Give master control module another chance if this is first call to
00141    * jpeg_write_raw_data.  This lets output of the frame/scan headers be
00142    * delayed so that application can write COM, etc, markers between
00143    * jpeg_start_compress and jpeg_write_raw_data.
00144    */
00145   if (cinfo->master->call_pass_startup)
00146     (*cinfo->master->pass_startup) (cinfo);
00147 
00148   /* Verify that at least one iMCU row has been passed. */
00149   lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->min_DCT_v_scaled_size;
00150   if (num_lines < lines_per_iMCU_row)
00151     ERREXIT(cinfo, JERR_BUFFER_SIZE);
00152 
00153   /* Directly compress the row. */
00154   if (! (*cinfo->coef->compress_data) (cinfo, data)) {
00155     /* If compressor did not consume the whole row, suspend processing. */
00156     return 0;
00157   }
00158 
00159   /* OK, we processed one iMCU row. */
00160   cinfo->next_scanline += lines_per_iMCU_row;
00161   return lines_per_iMCU_row;
00162 }