sp_uncompress.c

常用的无损压缩算法源代码

/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */

/*             S + P   I M A G E   D E C O M P R E S S I O N           */

/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */
/*     > > > > >    ANSI C version  3.06  -  05/30/95    < < < < <     */

/*                     Arithmetic code version                         */

/*   Amir Said - [e-mail]                            */
/*   Faculty of Electrical Engineering                                 */
/*   University of Campinas (UNICAMP) - Campinas, SP 13081, Brazil     */

/*   William A. Pearlman - [e-mail]                       */
/*   Dept. of Electrical, Computer, and Systems Engineering            */
/*   Rensselaer Polytechnic Institute - Troy, NY 12180, USA            */

/*     Copyright (c) 1995 Amir Said & William A. Pearlman              */

/*
   This program is Copyright (c) by Amir Said and William A. Pearlman.
   It may be freely redistributed in its entirety provided that this
   copyright notice is not removed. It may not be sold for profit or
   incorporated in commercial programs without the written permission
   of the copyright holders. This program is provided as is, without
   any express or implied warranty, without even the warranty of
   fitness for a particular purpose.
*/


/* - - Inclusion - - - - - - - - - - - - - - - - - - - - - - - - - - - */

#define KEY_1 0xA3

#include "arithm.h"
#include "sp_comm.c"
#include "sp_decd.c"


/* - - Definitions - - - - - - - - - - - - - - - - - - - - - - - - - - */

#define CondValues 5

#define CondModels 25


/* - - Static variables  - - - - - - - - - - - - - - - - - - - - - - - */

Adaptive_Model set_model[CondModels];


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* - - Implementations - - - - - - - - - - - - - - - - - - - - - - - - */

int Read_Value(Adaptive_Model * model, int * ns)
{
  int m, v, c, s = Read_Symbol(&code_file, model);
  *ns = s;

  if (!s) return 0;

  if ((m = set_table[s].bits) <= 10)
    c = Read_Bits(&code_file, m);
  else {
    c = Read_Bits(&code_file, 10);
    c |= Read_Bits(&code_file, m - 10) << 10; }

  v = (c >> 1) + set_table[s].bias;
  return (c & 1 ? -v : v);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

void Decode_First_Quadrant(Image_Coord d, int ** cf)
{
  int i, j, k;

  for (i = 0; i < d.x; i++)
    for (j = 0; j < d.y; j++)
      cf[i][j] = Read_Value(set_model, &k);

  Reset_Model(set_model);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

void Decode_Quadrant(int q, Image_Coord d, int ** cf)
{
  int i, j, k, mls, lm = CondValues - 1;
  int * ptr, * ps = buffer[0], * as = buffer[1], ls[4];
  Image_Coord min, max;

  Select_Quadrant(q, d, &min, &max);

  for (ls[0] = i = 0; i < d.x; i++) {

    if (!(i & 1)) {
      ptr = cf[(i+min.x)>>1] + (min.y >> 1);  ls[2] = Set(*ptr);  ++ptr;
      for (j = 2; j < d.y; j += 2) {
        ls[1] = ls[2];  ls[2] = Set(*ptr);  ++ptr;
        k = (ls[1] + ls[2] + 2) >> 2;
        ps[j-1] = ps[j] = CondValues * (k < lm ? k : lm); }
      ps[0] = ps[1];  ps[d.y-1] = ps[d.y-2]; }

    if (i) {
      ls[0] = ls[3] = as[0];  ls[2] = as[1];  as[d.y] = as[d.y-1]; }

    for (j = 0; j < d.y; j++) {
      if (i) {
        ls[1] = ls[2];  ls[2] = ls[3];  ls[3] = as[j+1];
        mls = (ls[0] + ls[1] + ls[2] + ls[3] + 4) >> 3; }
      else
        mls = ls[0] >> 1;
      mls = ps[j] + (mls < lm ? mls : lm);
      cf[i+min.x][j+min.y] = Read_Value(set_model + mls, ls);
      as[j] = ls[0]; } }
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

int ** Decode_Image(int lv, Image_Coord d)
{
  int ** cf, i, k;

  if ((cf = (int **) malloc(d.x * sizeof(int *))) == NULL)
    Error(m_msg);

  for (k = 0; k < d.x; k++)
    if ((cf[k] = (int *) malloc(d.y * sizeof(int))) == NULL)
      Error(m_msg);

  k = 1 + (d.x > d.y ? d.x : d.y);
  for (i = 0; i <= 1; i++)
    if ((buffer[i] = (int *) malloc(k * sizeof(int))) == NULL)
      Error(m_msg);

  k = Read_Bits(&code_file, 5);
  for (i = 0; i < CondModels; i++)
    Create_Model(set_model + i, k);

  d.x >>= --lv;  d.y >>= lv;

  Decode_First_Quadrant(d, cf);

  for (i = lv - 1; i >= 0; i--) {
    for (k = 1; k <= 3; k++) {
      Decode_Quadrant(k, d, cf); }
    d.x <<= 1;  d.y <<= 1; }

  return cf;
}


/* = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = */

/* end of file < sp_uncompress.c > */