regular_mode.cpp

来自「基于块方向的图像无损压缩代码」· C++ 代码 · 共 159 行

/*++*
* Copyright (c) 1997 University of British Columbia. All rights reserved.
*
*       File:           regular_mode.c
*       Pourpose:       contains the main routins used in the regular mode.
*
*       Author:         Ismaeil R. Ismaeil, Aug. 1997
*
*--*/
#include "stdafx.h"
#include "globals.h"
#include "prototypes.h"

void RegularModeProcessing()
{
	int i;//, j;

 /* Quantization of the gradients */
	for(i=0; i<3; i++)
	{
		if(D[i] <= -T3) 
			Q[i] = -4;
		else if(D[i] <= -T2) 
			Q[i] = -3;
		else if(D[i] <= -T1) 
			Q[i] = -2;
		else if(D[i] < -NEAR_LOSSLESS ) 
			Q[i] = -1;
		else if(D[i] <= NEAR_LOSSLESS) 
			Q[i] = 0;
		else if(D[i] < T1) 
			Q[i] = 1;
		else if(D[i] < T2) 
			Q[i] = 2;
		else if(D[i] < T3) 
			Q[i] = 3;
		else 
			Q[i] = 4;
	}

 /* Quantized gradient merging */

	if(Q[0] < 0)
	{
		Q[0] = -Q[0];
		Q[1] = -Q[1];
		Q[2] = -Q[2];
		SIGN = -1;
	}
	else if(Q[0]==0)
	{
		if(Q[1] < 0)
		{
			Q[1] = -Q[1];
			Q[2] = -Q[2];
			SIGN = -1;
		}
		else if(Q[1] == 0 && Q[2] < 0)
		{
			Q[2] = -Q[2];
			SIGN = -1;
		}
		else SIGN = 1;
	}
	else 
		SIGN = 1;

	/* The Maping step to detrmin Q */
	q = 81*Q[0] + 9*Q[1] + Q[2];

	/* Edg-detection predictor */
	if(Rc >= MAX(Ra,Rb))
		Px = MIN(Ra,Rb);
	else 
	{
		if(Rc <= MIN(Ra,Rb))
			Px = MAX(Ra,Rb);
		else
			Px = Ra + Rb - Rc;
	}
 
	/* Prediction correction */
 
	if(SIGN == 1)
		Px = Px + C[q];
	else
		Px = Px - C[q];

	if(Px > MAXVAL)
		Px = MAXVAL;
	else if(Px < 0)
		Px = 0;

	/* computation of prediction error */
 
	Errval = Ix - Px;
	if (SIGN == -1)
		Errval = -Errval;

	/* Error quantization for lossless mode, and reconstructed value */
	Rx = Ix; 

	/* Modulo reduction of the prediction error */
	Errval = ModRange(Errval, RANGE);

	/* Prediction error encoding */
	for(k=0; (N[q]<<k) < A[q]; k++);

	/* Error Mapping */
	if((NEAR_LOSSLESS == 0) && (k==0) && (2*B[q] <= -N[q])) 
	{
		if(Errval >= 0)
			MErrval = 2*Errval +1;
		else
			MErrval = -2*(Errval +1);
	}
	else
	{
		if(Errval >= 0)
			MErrval = 2*Errval;
		else
			MErrval = -2*Errval-1;
	}

	/* Mapped-error encoding */
	GolombCoding(MErrval, k, LIMIT);

	/* Update variables */
	B[q] = B[q] + Errval*(2*NEAR_LOSSLESS+1);
	A[q] = A[q] + ABS(Errval);
	if (N[q] == RESET) 
	{
		A[q] = A[q]>>1;
		B[q] = B[q]>>1;
		N[q] = N[q]>>1;
	}
	N[q] = N[q]+1;

	/* Contex-dependent bias computation */
	if(B[q] <= -N[q]) 
	{
		B[q] = B[q] + N[q];
		if(C[q] > MIN_C)//MIN_C=-128
			C[q] = C[q] - 1;
		if(B[q] <= -N[q])
			B[q] = -N[q] +1;
	}
	else if(B[q] > 0) 
	{
		B[q] = B[q] - N[q];
		if(C[q] < MAX_C)//MAX_C=127
			C[q] = C[q] + 1;
		if(B[q] > 0)
			B[q] = 0;
	}

	return;
}