jctrans.c

基于Linux的ffmepg decoder

/*
 * jctrans.c
 *
 * Copyright (C) 1995-1998, 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 library routines for transcoding compression,
 * that is, writing raw DCT coefficient arrays to an output JPEG file.
 * The routines in jcapimin.c will also be needed by a transcoder.
 */

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


/* Forward declarations */
//LOCAL(void) transencode_master_selection
//	JPP((j_compress_ptr cinfo, jvirt_barray_ptr * coef_arrays));
//LOCAL(void) transencode_coef_controller
//	JPP((j_compress_ptr cinfo, jvirt_barray_ptr * coef_arrays));


/*
 * Compression initialization for writing raw-coefficient data.
 * Before calling this, all parameters and a data destination must be set up.
 * Call jpeg_finish_compress() to actually write the data.
 *
 * The number of passed virtual arrays must match cinfo->num_components.
 * Note that the virtual arrays need not be filled or even realized at
 * the time write_coefficients is called; indeed, if the virtual arrays
 * were requested from this compression object's memory manager, they
 * typically will be realized during this routine and filled afterwards.
 */
#if 0
GLOBAL(void)
jpeg_write_coefficients (j_compress_ptr cinfo, jvirt_barray_ptr * coef_arrays)
{
  if (cinfo->global_state != CSTATE_START)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  /* Mark all tables to be written */
  jpeg_suppress_tables(cinfo, FALSE);
  /* (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 */
  transencode_master_selection(cinfo, coef_arrays);
  /* Wait for jpeg_finish_compress() call */
  cinfo->next_scanline = 0;	/* so jpeg_write_marker works */
  cinfo->global_state = CSTATE_WRCOEFS;
}


/*
 * Master selection of compression modules for transcoding.
 * This substitutes for jcinit.c's initialization of the full compressor.
 */

LOCAL(void)
transencode_master_selection (j_compress_ptr cinfo,
			      jvirt_barray_ptr * coef_arrays)
{
  /* Although we don't actually use input_components for transcoding,
   * jcmaster.c's initial_setup will complain if input_components is 0.
   */
  cinfo->input_components = 1;
  /* Initialize master control (includes parameter checking/processing) */
  jinit_c_master_control(cinfo, TRUE /* transcode only */);
#if 0
  /* Entropy encoding: either Huffman or arithmetic coding. */
  if (cinfo->arith_code) {
    ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
  } else {
    if (cinfo->progressive_mode) {
#ifdef C_PROGRESSIVE_SUPPORTED
//      jinit_phuff_encoder(cinfo);
#else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
    } else
#endif
	//only support huffman coding
      jinit_huff_encoder(cinfo);

  //}

  /* We need a special coefficient buffer controller. */
  //transencode_coef_controller(cinfo, coef_arrays);

  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, JFIF) immediately.
   * Frame and scan headers are postponed till later.
   * This lets application insert special markers after the SOI.
   */
  //(*cinfo->marker->write_file_header) (cinfo);
  write_file_header1(cinfo);
}
#endif

/*
 * The rest of this file is a special implementation of the coefficient
 * buffer controller.  This is similar to jccoefct.c, but it handles only
 * output from presupplied virtual arrays.  Furthermore, we generate any
 * dummy padding blocks on-the-fly rather than expecting them to be present
 * in the arrays.
 */

/* Private buffer controller object */
#if 0
typedef struct {
  struct jpeg_c_coef_controller pub; /* public fields */

  JDIMENSION iMCU_row_num;	/* iMCU row # within image */
  JDIMENSION mcu_ctr;		/* counts MCUs processed in current row */
  int MCU_vert_offset;		/* counts MCU rows within iMCU row */
  int MCU_rows_per_iMCU_row;	/* number of such rows needed */

  /* Virtual block array for each component. */
  jvirt_barray_ptr * whole_image;

  /* Workspace for constructing dummy blocks at right/bottom edges. */
  JBLOCKROW dummy_buffer[C_MAX_BLOCKS_IN_MCU];
} my_coef_controller;

typedef my_coef_controller * my_coef_ptr;


LOCAL(void)
start_iMCU_row (j_compress_ptr cinfo)
/* Reset within-iMCU-row counters for a new row */
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  /* In an interleaved scan, an MCU row is the same as an iMCU row.
   * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
   * But at the bottom of the image, process only what's left.
   */
  if (cinfo->comps_in_scan > 1) {
    coef->MCU_rows_per_iMCU_row = 1;
  } else {
    if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
    else
      coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
  }

  coef->mcu_ctr = 0;
  coef->MCU_vert_offset = 0;
}
#endif

/*
 * Initialize for a processing pass.
 */
#if 0
METHODDEF(void)
start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
{
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

  if (pass_mode != JBUF_CRANK_DEST)
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

  coef->iMCU_row_num = 0;
  start_iMCU_row(cinfo);
}
#endif



/*
 * Initialize coefficient buffer controller.
 *
 * Each passed coefficient array must be the right size for that
 * coefficient: width_in_blocks wide and height_in_blocks high,
 * with unitheight at least v_samp_factor.
 */
#if 0
LOCAL(void)
transencode_coef_controller (j_compress_ptr cinfo,
			     jvirt_barray_ptr * coef_arrays)
{
  my_coef_ptr coef;
  JBLOCKROW buffer;
  int i;

  //coef = (my_coef_ptr)
  //  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
  //				SIZEOF(my_coef_controller));
  cinfo->coef = (struct jpeg_c_coef_controller *) coef;
  coef->pub.start_pass = start_pass_coef;
  
  //coef->pub.compress_data = compress_output;

  /* Save pointer to virtual arrays */
  //coef->whole_image = coef_arrays;

#if 0
  /* Allocate and pre-zero space for dummy DCT blocks. */
  buffer = (JBLOCKROW)
    (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));   //local mem
  jzero_far((void FAR *) buffer, C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
  for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
    coef->dummy_buffer[i] = buffer + i;
  }
#endif
}
#endif