jcinit.c

00001 /*
00002  * jcinit.c
00003  *
00004  * Copyright (C) 1991-1997, Thomas G. Lane.
00005  * Modified 2003-2013 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 initialization logic for the JPEG compressor.
00010  * This routine is in charge of selecting the modules to be executed and
00011  * making an initialization call to each one.
00012  *
00013  * Logically, this code belongs in jcmaster.c.  It's split out because
00014  * linking this routine implies linking the entire compression library.
00015  * For a transcoding-only application, we want to be able to use jcmaster.c
00016  * without linking in the whole library.
00017  */
00018 
00019 #define JPEG_INTERNALS
00020 #include "jinclude.h"
00021 #include "jpeglib.h"
00022 
00023 
00024 /*
00025  * Master selection of compression modules.
00026  * This is done once at the start of processing an image.  We determine
00027  * which modules will be used and give them appropriate initialization calls.
00028  */
00029 
00030 GLOBAL(void)
00031 jinit_compress_master (j_compress_ptr cinfo)
00032 {
00033   long samplesperrow;
00034   JDIMENSION jd_samplesperrow;
00035 
00036   /* For now, precision must match compiled-in value... */
00037   if (cinfo->data_precision != BITS_IN_JSAMPLE)
00038     ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
00039 
00040   /* Sanity check on image dimensions */
00041   if (cinfo->image_height <= 0 || cinfo->image_width <= 0 ||
00042       cinfo->input_components <= 0)
00043     ERREXIT(cinfo, JERR_EMPTY_IMAGE);
00044 
00045   /* Width of an input scanline must be representable as JDIMENSION. */
00046   samplesperrow = (long) cinfo->image_width * (long) cinfo->input_components;
00047   jd_samplesperrow = (JDIMENSION) samplesperrow;
00048   if ((long) jd_samplesperrow != samplesperrow)
00049     ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
00050 
00051   /* Initialize master control (includes parameter checking/processing) */
00052   jinit_c_master_control(cinfo, FALSE /* full compression */);
00053 
00054   /* Preprocessing */
00055   if (! cinfo->raw_data_in) {
00056     jinit_color_converter(cinfo);
00057     jinit_downsampler(cinfo);
00058     jinit_c_prep_controller(cinfo, FALSE /* never need full buffer here */);
00059   }
00060   /* Forward DCT */
00061   jinit_forward_dct(cinfo);
00062   /* Entropy encoding: either Huffman or arithmetic coding. */
00063   if (cinfo->arith_code)
00064     jinit_arith_encoder(cinfo);
00065   else {
00066     jinit_huff_encoder(cinfo);
00067   }
00068 
00069   /* Need a full-image coefficient buffer in any multi-pass mode. */
00070   jinit_c_coef_controller(cinfo,
00071         (boolean) (cinfo->num_scans > 1 || cinfo->optimize_coding));
00072   jinit_c_main_controller(cinfo, FALSE /* never need full buffer here */);
00073 
00074   jinit_marker_writer(cinfo);
00075 
00076   /* We can now tell the memory manager to allocate virtual arrays. */
00077   (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
00078 
00079   /* Write the datastream header (SOI) immediately.
00080    * Frame and scan headers are postponed till later.
00081    * This lets application insert special markers after the SOI.
00082    */
00083   (*cinfo->marker->write_file_header) (cinfo);
00084 }