coder_sm.c

基于小波的图像压缩

/*****

SigMap : send "significance map" then residual values

	the sigmap is a mask of five entries : "0,1,-1, positive > 1, negative < -1"
		it is order-1 context coded bases on the the parents' sigmap entry.
	if one of the later two escapes is sent, their magnitude is coded (the residual)
		with an order-1 context coder based on the parents MSB (log2 of value)
		(we use a truncated alphabet then do order-minus-1 on the rest)

	could try better ways to code residuals

-----

S+P Lena lossless : 4.255 bpp

******/

#include <stdio.h>
#include <stdlib.h>
#include <crblib/inc.h>
#include <crblib/arithc.h>
#include <crblib/scontext.h>
#include <crblib/o0coder.h>

extern int tune_param;

/*** some convenient debug routines:
** #define SEND_TAG()	if(0); else { arithEncode(ari,43,44,77); }
** #define GET_TAG()	if(0); else { int got; got = arithGet(ari,77); arithDecode(ari,43,44,77); if ( got != 43 ) errexit("tag failure"); }
********/

#define CNTX_CAP			10	/** I'm very surprised that this tunes so high! **/
#define SIGMAP_CONTEXTS		(CNTX_CAP+CNTX_CAP+1)
#define SIGMAP_ALPHABET		5	/** 0,1,-1,pos,neg **/

#define SIGMAP_TOTMAX		5000
#define SIGMAP_INC			30

#define ORDER0_CNTXMAX		8
#define ORDER0_CONTEXTS		(ORDER0_CNTXMAX+1)
#define ORDER0_TOTMAX		500
#define ORDER0_ALPHABET		25
#define ORDER0_ESCAPE		(ORDER0_ALPHABET-1)

#include "coder.h"

void coderSigMap_encodeBand(coder *me,int *band,int w,int h,int fullw,int *parent);
void coderSigMap_decodeBand(coder *me,int *band,int w,int h,int fullw,int *parent);

typedef struct {
	ozero ** o0;
	scontext ** o1;
} myInfo;

void coderSigMap_init(coder *c)
{
myInfo *d;
int i;

	if ( (d = new(myInfo)) == NULL )
		errexit("ozero init failed");

	c->data = d;

	if ( (d->o0 = newarray(void *,ORDER0_CONTEXTS)) == NULL )
		errexit("Order0_Init failed!");

	for(i=0;i<ORDER0_CONTEXTS;i++)
		if ( (d->o0[i] = ozeroCreateMax(c->arith,ORDER0_ALPHABET,ORDER0_TOTMAX)) == NULL )
			errexit("ozero init failed");

	if ( (d->o1 = newarray(void *,SIGMAP_CONTEXTS)) == NULL )
		errexit("Order1_Init failed!");

	for(i=0;i<SIGMAP_CONTEXTS;i++)
		if ( (d->o1[i] = scontextCreate(c->arith,SIGMAP_ALPHABET,0,
				SIGMAP_TOTMAX,SIGMAP_INC,true)) == NULL )
			errexit("context creation failed!");

}

void coderSigMap_free(coder *c)
{
	if ( c->data ) {
		myInfo *d;
		d = c->data;
		if ( d->o0 ) {
			int i;
			for(i=0;i<ORDER0_CONTEXTS;i++)
				if ( d->o0[i] ) ozeroFree(d->o0[i]);
			free(d->o0);
		}
		if ( d->o1 ) {
			int i;
			for(i=0;i<SIGMAP_CONTEXTS;i++) {
				if ( d->o1[i] ) scontextFree(d->o1[i]);
			}
		}
		free(d);
		c->data = NULL;
	}
}

coder coderSigMap = {
		"SigMap",
		coderSigMap_init,
		coderSigMap_free,
		coderSigMap_encodeBand,
		coderSigMap_decodeBand
	};

void coderSigMap_encodeBand(coder *me,int *band,int width,int height,int fullw,int *parent)
{
int x,y,val,cntx;
int *dp,*pp;
int par_val,par_sig;
ozero **o0 = ((myInfo *)me->data)->o0;
scontext **o1 = ((myInfo *)me->data)->o1;
arithInfo *ari = me->arith;

	dp = band;	pp = parent;
	for(y=0;y<height;y++) {
		if ( coder_timetostop(me) ) { coder_didstop(me,y); return; }
		for(x=0;x<width;x++) {
			par_sig = pp[x>>1]; par_val = abs(par_sig);
			par_sig = max(- CNTX_CAP,min(CNTX_CAP,par_sig)); par_sig += CNTX_CAP;

			val = dp[x];	
			switch(val) {
				case 0:		scontextEncode(o1[par_sig],0); break;
				case 1:		scontextEncode(o1[par_sig],1); break;
				case -1:	scontextEncode(o1[par_sig],2); break;
				default:
					if ( isneg(val) ){	scontextEncode(o1[par_sig],3); val = -val; }
					else 				scontextEncode(o1[par_sig],4);
					val -= 2;
					cntx = min(ORDER0_CNTXMAX, intlog2(par_val) );
					if ( val < ORDER0_ESCAPE ) ozeroEncode(o0[cntx],val);
					else {
						ozeroEncode(o0[cntx],ORDER0_ESCAPE);
						encode_m1(ari,val - ORDER0_ESCAPE);
					}
					break;
			}
		}
		if ( y&1 ) pp += fullw;
		dp += fullw;
	}
}

void coderSigMap_decodeBand(coder *me,int *band,int width,int height,int fullw,int *parent)
{
int x,y,val,cntx,sign;
int *dp,*pp;
int par_val,par_sig;
ozero **o0 = ((myInfo *)me->data)->o0;
scontext **o1 = ((myInfo *)me->data)->o1;
arithInfo *ari = me->arith;

	dp = band;	pp = parent;
	for(y=0;y<height;y++) {
		if ( coder_timetostopd(me,y) ) return;
		for(x=0;x<width;x++) {
			par_sig = pp[x>>1]; par_val = abs(par_sig);
			par_sig = max(- CNTX_CAP,min(CNTX_CAP,par_sig)); par_sig += CNTX_CAP;

			switch( scontextDecode(o1[par_sig]) ) {
				case 0:		dp[x] = 0; break;
				case 1:		dp[x] = 1; break;
				case 2:		dp[x] = -1; break;
				case 3:		sign = -1; goto decode_val;
				case 4:		sign = 1;
				decode_val:
					cntx = min(ORDER0_CNTXMAX, intlog2(par_val) );
					val = ozeroDecode(o0[cntx]);
					if( val == ORDER0_ESCAPE ) val += decode_m1(ari);
					dp[x] = sign * (val + 2);
					break;
				default: 	
					errexit("decoded past alphabet!");
			}
		}
		if ( y&1 ) pp += fullw;
		dp += fullw;
	}
}