# dlib C++ Library - jcinit.c

    /*
     * jcinit.c
     *
     * Copyright (C) 1991-1997, 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 initialization logic for the JPEG compressor.
     * This routine is in charge of selecting the modules to be executed and
     * making an initialization call to each one.
     *
     * Logically, this code belongs in jcmaster.c.  It's split out because
     * linking this routine implies linking the entire compression library.
     * For a transcoding-only application, we want to be able to use jcmaster.c
     * without linking in the whole library.
     */

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

    /*
     * 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.
     */

    GLOBAL(void)
    jinit_compress_master (j_compress_ptr cinfo)
    {
      /* Initialize master control (includes parameter checking/processing) */
      jinit_c_master_control(cinfo, FALSE /* full compression */);

      /* 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)
        jinit_arith_encoder(cinfo);
      else {
        jinit_huff_encoder(cinfo);
      }

      /* Need a full-image coefficient buffer in any multi-pass mode. */
      jinit_c_coef_controller(cinfo,
    		(boolean) (cinfo->num_scans > 1 || 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);
    }